U.S. patent application number 16/288944 was filed with the patent office on 2019-06-27 for hydraulic system for work machine.
This patent application is currently assigned to KUBOTA CORPORATION. The applicant listed for this patent is KUBOTA CORPORATION. Invention is credited to Kazuyoshi ARII, Yuji FUKUDA, Ryohei SUMIYOSHI.
Application Number | 20190195207 16/288944 |
Document ID | / |
Family ID | 60483696 |
Filed Date | 2019-06-27 |
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United States Patent
Application |
20190195207 |
Kind Code |
A1 |
FUKUDA; Yuji ; et
al. |
June 27, 2019 |
HYDRAULIC SYSTEM FOR WORK MACHINE
Abstract
A hydraulic system for a work machine includes an operation
member, a prime mover, a hydraulic pump driven by the prime mover,
the hydraulic pump configured to output an operation fluid, a first
temperature sensor to measure a temperature of the operation fluid,
a first fluid tube connected to the hydraulic pump, an operation
valve connected to the first fluid tube, the operation valve
configured to control, in accordance with an operation extent of
the operation member, a pressure of the outputted operation fluid,
a hydraulic apparatus driven by the operation fluid outputted from
the operation valve, a second hydraulic tube connecting the
operation valve to the hydraulic apparatus, a discharge fluid tube
to discharge the operation fluid included in the second fluid tube;
and an actuation valve disposed on the discharge fluid tube, the
actuation valve configured to control an aperture of the actuation
valve based on the temperature.
Inventors: |
FUKUDA; Yuji; (Osaka,
JP) ; ARII; Kazuyoshi; (Osaka, JP) ;
SUMIYOSHI; Ryohei; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KUBOTA CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
KUBOTA CORPORATION
Osaka
JP
|
Family ID: |
60483696 |
Appl. No.: |
16/288944 |
Filed: |
February 28, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15615056 |
Jun 6, 2017 |
10280906 |
|
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16288944 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/2285 20130101;
F04B 1/26 20130101; E02F 9/2292 20130101; E02F 3/3414 20130101;
E02F 9/2025 20130101; E02F 9/166 20130101 |
International
Class: |
F04B 1/26 20060101
F04B001/26; E02F 9/22 20060101 E02F009/22; E02F 9/20 20060101
E02F009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2016 |
JP |
2016-113600 |
Dec 28, 2016 |
JP |
2016-255462 |
Dec 28, 2016 |
JP |
2016-255463 |
Claims
1. A hydraulic system for a work machine comprising: an operation
member; a hydraulic pump to output an operation fluid; a first
fluid tube connected to the hydraulic pump; an operation valve
disposed on the first fluid tube, the operation valve being
configured to control, in accordance with an operation extent of
the operation member, a pressure of the operation fluid to be
outputted; a hydraulic apparatus to be driven by the operation
fluid outputted from the operation valve; a second hydraulic tube
connecting the operation valve to the hydraulic apparatus; an
actuation valve disposed on the first fluid tube between the
operation valve and the hydraulic pump; a third fluid tube
connecting the second fluid tube to an intermediate section of the
first fluid tube between the operation valve and the actuation
valve; and a check valve disposed on the third fluid tube, the
check valve being configured to supply the operation fluid from the
second fluid tube to the first fluid tube and block the operation
fluid flowing from the first fluid tube to the second fluid
tube.
2. The hydraulic system according to claim 1, comprising a throttle
disposed between the operation valve and a portion of the second
fluid tube, the portion being connected to the third fluid.
3. A hydraulic system for a work machine comprising: an operation
member to be moved to one direction and to the other direction; a
hydraulic pump to output an operation fluid; a first fluid tube
connected to the hydraulic pump; a first operation valve connected
to the first fluid tube, the first operation valve being configured
to control, in accordance with the movement to the one direction of
the operation member, a pressure of the operation fluid to be
outputted; a second operation valve connected to the first fluid
tube, the first operation valve being configured to control, in
accordance with the movement to the other direction of the
operation member, a pressure of the operation fluid to be
outputted; a hydraulic apparatus to be driven by the operation
fluid outputted from the first operation valve or from the second
operation valve; and a pressure changer to differentiate a pressure
of the operation fluid that is supplied from the first operation
valve to the hydraulic apparatus when the operation member is moved
to the one direction from a pressure of the operation fluid that is
supplied from the second operation valve to the hydraulic apparatus
when the operation member is moved to the other direction.
4. A hydraulic system for a work machine comprising: an operation
member to be moved to a first direction and to a second direction
perpendicular to the first direction; a hydraulic pump to output an
operation fluid; a first fluid tube connected to the hydraulic
pump; a first operation valve connected to the first fluid tube,
the first operation valve being configured to control, in
accordance with the movement to one direction in the first
direction of the operation member, a pressure of the operation
fluid to be outputted; a second operation valve connected to the
first fluid tube, the first operation valve being configured to
control, in accordance with the movement to the other direction in
the first direction of the operation member, a pressure of the
operation fluid to be outputted; a third operation valve connected
to the first fluid tube, the first operation valve being configured
to control, in accordance with the movement to one direction in the
second direction of the operation member, a pressure of the
operation fluid to be outputted; a fourth operation valve connected
to the first fluid tube, the first operation valve being configured
to control, in accordance with the movement to the other direction
in the second direction of the operation member, a pressure of the
operation fluid to be outputted; a hydraulic apparatus to be driven
by the operation fluid outputted from at least one of the first
operation valve, the second operation valve, the third operation
valve, and the fourth operation valve; and a pressure changer to
differentiate a pressure of the operation fluid that is supplied
from the first operation valve or the second operation valve to the
hydraulic apparatus when the operation member is moved to the first
direction from a pressure of the operation fluid that is supplied
from the third operation valve or the fourth operation valve to the
hydraulic apparatus when the operation member is moved to the
second direction.
5. The hydraulic system according to claim 4, wherein the hydraulic
apparatus is a travel device to travel forward, backward,
rightward, and leftward, the first operation valve is a valve to
output the operation fluid for the forward traveling to the travel
device, the second operation valve is a valve to output the
operation fluid for the backward traveling to the travel device,
the third operation valve is a valve to output the operation fluid
for the rightward traveling to the travel device, and the fourth
operation valve is a valve to output the operation fluid for the
leftward traveling to the travel device.
6. The hydraulic system according to claim 5, wherein the pressure
changer includes a first variable relief valve connected to the
first operation valve, the first variable relief valve having a
pressure-receiving portion to receive the pressure outputted from
the third operation valve, and a second variable relief valve
connected to the second operation valve, the first variable relief
valve having a pressure-receiving portion to receive the pressure
outputted from the fourth operation valve.
7. A hydraulic system for a work machine comprising: a hydraulic
pump to output an operation fluid; a first hydraulic fluid
connected to the hydraulic pump; a travel device to be activated by
the operation fluid; a first operation device connected to the
travel device, including a first operation member to be moved to
one direction and to the other direction, a first operation valve
connected to the first fluid tube, the first operation valve being
configured to control, in accordance with the movement to the one
direction of the first operation member, a pressure of the
operation fluid, and a second operation valve connected to the
first fluid tube, the first operation valve being configured to
control, in accordance with the movement to the other direction of
the first operation member, the pressure of the operation fluid; a
second operation device connected to the travel device, the second
operation device being other than the first operation device,
including a second operation member to be moved to one direction
and to the other direction, a third operation valve connected to
the first fluid tube, the third operation valve being configured to
control, in accordance with the movement to the one direction of
the second operation member, the pressure of the operation fluid,
and a fourth operation valve connected to the first fluid tube, the
fourth operation valve being configured to control, in accordance
with the movement to the other direction of the second operation
member, the pressure of the operation fluid; a first select valve
including an output port to output higher any one of the pressure
of the operation fluid outputted from the first operation valve and
the pressure of the operation fluid outputted from the third
operation valve; a second select valve including an output port to
output higher any one of the pressure of the operation fluid
outputted from the second operation valve and the pressure of the
operation fluid outputted from the fourth operation valve; a third
select valve including an output port to output higher any one of
the pressure of the operation fluid outputted from the output port
of the first operation valve and the pressure of the operation
fluid outputted from the output port of the second operation valve;
a fourth fluid tube connected to the output port of the third
select valve; and a brake device connected to the fourth fluid
tube, the brake device to release a braking state of the travel
device when the pressure of the operation fluid is applied to the
brake device.
8. The hydraulic system according to claim 7, comprising: a fifth
fluid tube connected to an intermediate portion of the fourth fluid
tube; and a switch valve connected to the fifth fluid tube, the
switch valve being configured to be switched to discharge the
operation fluid included in the fifth fluid tube.
9. The hydraulic system according to claim 7, comprising a first
check valve disposed on the fourth fluid tube, the first check
valve being configured to supply the operation fluid from the third
select valve to the brake device and block the operation fluid
flowing from the brake device to the third select valve.
10. The hydraulic system according to claim 9, comprising a second
check valve to supply the operation fluid from a side of the first
check valve to the switch valve and block the operation fluid
flowing from the switch valve to the side of the first check
valve.
11. The hydraulic system according to claim 7, comprising a switch
to switch the switch valve between a side to discharge the
operation fluid included in the fourth fluid tube and a side not to
discharge the operation fluid included in the fourth fluid tube.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of co-pending
application Ser. No. 15/615,056, filed Jun. 6, 2017, which claims
priority under 35 U.S.C. .sctn. 119 to Japanese Patent Application
No. 2016-113600, filed Jun. 7, 2016, to Japanese Patent Application
No. 2016-255462, filed Dec. 28, 2016, to Japanese Patent
Application No. 2016-255463, filed Dec. 28, 2016. The contents of
each of these U.S. and Japanese applications are incorporated
herein by reference in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a hydraulic system for a
work machine.
Discussion of the Background
[0003] Japanese patent application publication No. 2013-117253
disclosed a conventional technique for warming up a work
machine.
[0004] The work machine disclosed in Japanese patent application
publication No. 2013-117253 includes a pilot pressure control valve
configured to control a pressure of a pilot fluid that is outputted
from a pump to be supplied to a target device and includes a valve
body incorporating the pilot pressure control valve. The technique
disclosed in Japanese patent application publication No.
2013-117253 disposes a heat-up fluid tube on the valve body, the
heat-up fluid tube being configured to supply the pilot fluid
outputted from the pump. In this manner, the technique supplies the
pilot fluid passing through the heat-up fluid tube to an operation
fluid tank through a relief valve or a throttle, and thereby
heating up the valve body.
[0005] In addition, a work machine disclosed in Japanese patent
application publication No. 2013-36274 includes an engine, an HST
pump configured to be driven by a motive power of the engine, a
travel operation device configured to operate the HST pump, a
pressure control valve configured to control a travel primary
pressure that is a pressure on a primary side of the travel
operation device, and a control device to control the pressure
control valve.
[0006] The control device controls the pressure control valve on
the basis of a no-load characteristic line employed when a load is
free and a drop characteristic line employed when a predetermined
load or more is applied to the engine, thereby preventing the
engine stall.
[0007] Japanese patent publication No. 5687970 reduces an output
power of a travel pump when a predetermined load or more is applied
to the engine, the travel pump being one of hydraulic devices. In
particular, a work machine disclosed in Japanese patent publication
No. 5687970 includes an engine, a travel pump configured to be
driven by the engine, a travel operation lever, an operation valve
configured to change a pressure of a pilot fluid (a pilot pressure)
in accordance with operation of the travel operation lever, and a
pressure control valve disposed on an upper stream side of the
operation valve.
[0008] A work machine disclosed in Japanese patent application
publication No. 2016-148446 includes an operation valve configured
to change a pressure of an operation fluid in accordance with an
operation amount of an operation lever, a travel pump configured to
change an output power on the basis of the pressure of the
operation fluid changed by the operation valve, and travel motor
configured to be driven by the operation fluid outputted from the
travel pump.
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] A hydraulic system for a work machine includes an operation
member, a prime mover, a hydraulic pump to be driven by the prime
mover, the hydraulic pump being configured to output an operation
fluid, a first temperature sensor to measure a temperature of the
operation fluid, a first fluid tube connected to the hydraulic
pump, an operation valve connected to the first fluid tube, the
operation valve being configured to control, in accordance with an
operation extent of the operation member, a pressure of the
operation fluid to be outputted, a hydraulic apparatus to be driven
by the operation fluid outputted from the operation valve, a second
hydraulic tube connecting the operation valve to the hydraulic
apparatus, a discharge fluid tube to discharge the operation fluid
included in the second fluid tube; and an actuation valve disposed
on the discharge fluid tube, the actuation valve being configured
to control an aperture of the actuation valve based on the
temperature.
[0010] A hydraulic system for a work machine includes an operation
member, a hydraulic pump to output an operation fluid, a first
fluid tube connected to the hydraulic pump, an operation valve
disposed on the first fluid tube, the operation valve being
configured to control, in accordance with an operation extent of
the operation member, a pressure of the operation fluid to be
outputted, a hydraulic apparatus to be driven by the operation
fluid outputted from the operation valve, a second hydraulic tube
connecting the operation valve to the hydraulic apparatus, an
actuation valve disposed on the first fluid tube between the
operation valve and the hydraulic pump, a third fluid tube
connecting the second fluid tube to an intermediate section of the
first fluid tube between the operation valve and the actuation
valve, and a check valve disposed on the third fluid tube, the
check valve being configured to supply the operation fluid from the
second fluid tube to the first fluid tube and block the operation
fluid flowing from the first fluid tube to the second fluid
tube.
[0011] A hydraulic system for a work machine includes an operation
member to be moved to one direction and to the other direction, a
hydraulic pump to output an operation fluid;
[0012] a first fluid tube connected to the hydraulic pump, a first
operation valve connected to the first fluid tube, the first
operation valve being configured to control, in accordance with the
movement to the one direction of the operation member, a pressure
of the operation fluid to be outputted, a second operation valve
connected to the first fluid tube, the first operation valve being
configured to control, in accordance with the movement to the other
direction of the operation member, a pressure of the operation
fluid to be outputted, a hydraulic apparatus to be driven by the
operation fluid outputted from the first operation valve or from
the second operation valve, and a pressure changer to differentiate
a pressure of the operation fluid that is supplied from the first
operation valve to the hydraulic apparatus when the operation
member is moved to the one direction from a pressure of the
operation fluid that is supplied from the second operation valve to
the hydraulic apparatus when the operation member is moved to the
other direction.
[0013] A hydraulic system for a work machine includes an operation
member to be moved to a first direction and to a second direction
perpendicular to the first direction, a hydraulic pump to output an
operation fluid, a first fluid tube connected to the hydraulic
pump, a first operation valve connected to the first fluid tube,
the first operation valve being configured to control, in
accordance with the movement to one direction in the first
direction of the operation member, a pressure of the operation
fluid to be outputted, a second operation valve connected to the
first fluid tube, the first operation valve being configured to
control, in accordance with the movement to the other direction in
the first direction of the operation member, a pressure of the
operation fluid to be outputted, a third operation valve connected
to the first fluid tube, the first operation valve being configured
to control, in accordance with the movement to one direction in the
second direction of the operation member, a pressure of the
operation fluid to be outputted, a fourth operation valve connected
to the first fluid tube, the first operation valve being configured
to control, in accordance with the movement to the other direction
in the second direction of the operation member, a pressure of the
operation fluid to be outputted, a hydraulic apparatus to be driven
by the operation fluid outputted from at least one of the first
operation valve, the second operation valve, the third operation
valve, and the fourth operation valve, and a pressure changer to
differentiate a pressure of the operation fluid that is supplied
from the first operation valve or the second operation valve to the
hydraulic apparatus when the operation member is moved to the first
direction from a pressure of the operation fluid that is supplied
from the third operation valve or the fourth operation valve to the
hydraulic apparatus when the operation member is moved to the
second direction.
[0014] A hydraulic system for a work machine includes a hydraulic
pump to output an operation fluid, a first hydraulic fluid
connected to the hydraulic pump, a travel device to be activated by
the operation fluid, a first operation device connected to the
travel device, including a first operation member to be moved to
one direction and to the other direction, a first operation valve
connected to the first fluid tube, the first operation valve being
configured to control, in accordance with the movement to the one
direction of the first operation member, a pressure of the
operation fluid, and a second operation valve connected to the
first fluid tube, the first operation valve being configured to
control, in accordance with the movement to the other direction of
the first operation member, the pressure of the operation fluid, a
second operation device connected to the travel device, the second
operation device being other than the first operation device,
including a second operation member to be moved to one direction
and to the other direction, a third operation valve connected to
the first fluid tube, the third operation valve being configured to
control, in accordance with the movement to the one direction of
the second operation member, the pressure of the operation fluid,
and a fourth operation valve connected to the first fluid tube, the
fourth operation valve being configured to control, in accordance
with the movement to the other direction of the second operation
member, the pressure of the operation fluid, a first select valve
including an output port to output higher any one of the pressure
of the operation fluid outputted from the first operation valve and
the pressure of the operation fluid outputted from the third
operation valve, a second select valve including an output port to
output higher any one of the pressure of the operation fluid
outputted from the second operation valve and the pressure of the
operation fluid outputted from the fourth operation valve, a third
select valve including an output port to output higher any one of
the pressure of the operation fluid outputted from the output port
of the first operation valve and the pressure of the operation
fluid outputted from the output port of the second operation valve,
a fourth fluid tube connected to the output port of the third
select valve, and a brake device connected to the fourth fluid
tube, the brake device to release a braking state of the travel
device when the pressure of the operation fluid is applied to the
brake device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0016] FIG. 1 is a view illustrating a hydraulic system for travel
(a hydraulic circuit) for a work machine according to a first
embodiment of the present invention;
[0017] FIG. 2 is a view illustrating a hydraulic system for work (a
hydraulic circuit) for the work machine according to the first
embodiment;
[0018] FIG. 3 is a view illustrating a relation between an engine
revolution speed, a travel primary pressure, and a control line
according to the first embodiment;
[0019] FIG. 4 is a view illustrating a hydraulic system for travel
(a hydraulic circuit) for a work machine according to a second
embodiment of the present invention;
[0020] FIG. 5 is a view illustrating a hydraulic system for travel
(a hydraulic circuit) for a work machine according to a third
embodiment of the present invention;
[0021] FIG. 6 is a view illustrating a hydraulic system for travel
(a hydraulic circuit) for a work machine according to a fourth
embodiment of the present invention;
[0022] FIG. 7 is a view illustrating a hydraulic system for work (a
hydraulic circuit) for a work machine according to the fourth
embodiment;
[0023] FIG. 8A is a view illustrating a relation between an
operation device, a travel fluid tube, a select valve, and a brake
device according to the fourth embodiment;
[0024] FIG. 8B is a view illustrating a first modified example of
the relation between the operation device, the travel fluid tube,
the select valve, and the brake device according to the fourth
embodiment;
[0025] FIG. 8C is a view illustrating a second modified example of
the relation between the operation device, the travel fluid tube,
the select valve, and the brake device according to the fourth
embodiment;
[0026] FIG. 9A is a view illustrating a relation between an engine
revolution speed, a travel secondary pressure, and a control line
according to the fourth embodiment;
[0027] FIG. 9B is a view illustrating a case where the travel
secondary pressure has an upper limitation;
[0028] FIG. 10 is a schematic view illustrating a hydraulic system
for travel (a hydraulic circuit) according to a fifth embodiment of
the present invention;
[0029] FIG. 11 is a schematic view illustrating a hydraulic system
for work (a hydraulic circuit) according to the fifth
embodiment;
[0030] FIG. 12A is a view illustrating a first modified example of
the hydraulic system according to the fifth embodiment;
[0031] FIG. 12B is a view illustrating a second modified example of
the hydraulic system according to the fifth embodiment;
[0032] FIG. 13 is a schematic view illustrating a hydraulic system
for travel (a hydraulic circuit) according to a sixth embodiment of
the present invention;
[0033] FIG. 14 is a schematic view illustrating a hydraulic system
for work (a hydraulic circuit) according to the sixth
embodiment;
[0034] FIG. 15 is a view illustrating a relation between an engine
revolution speed, an oil temperature, and a set pressure of a
relief valve (a temperature-restricting pressure) according to the
sixth embodiment;
[0035] FIG. 16 is a schematic view illustrating a first modified
example of the hydraulic system for travel according to the sixth
embodiment;
[0036] FIG. 17 is a view a view illustrating a relation between the
engine revolution speed, the oil temperature, and a set pressure of
the relief valve (a travel-restricting pressure, the
temperature-restricting pressure) according to the sixth
embodiment;
[0037] FIG. 18 is a schematic view illustrating a second modified
example of the hydraulic system for travel according to the sixth
embodiment;
[0038] FIG. 19 is a view illustrating a relation between the engine
revolution speed, the oil temperature, and a set pressure of the
relief valve (a revolution-restricting pressure, the
temperature-restricting pressure) according to the sixth
embodiment;
[0039] FIG. 20 is a schematic view illustrating a hydraulic system
for work according to a seventh embodiment of the present
invention;
[0040] FIG. 21 is a side view illustrating a track loader
exemplified as a work machine according to the embodiments of the
present invention; and
[0041] FIG. 22 is a side view illustrating a part of the track
loader lifting up a cabin according to the embodiments.
DESCRIPTION OF THE EMBODIMENTS
[0042] The embodiments will now be described with reference to the
accompanying drawings, wherein like reference numerals designate
corresponding or identical elements throughout the various
drawings. The drawings are to be viewed in an orientation in which
the reference numerals are viewed correctly.
[0043] Referring to drawings, a hydraulic system and a work machine
having the hydraulic system according to embodiments of the present
invention will be described below.
First Embodiment
[0044] FIG. 20 illustrates a side view of a work machine according
to a first embodiment of the present invention. FIG. 20 illustrates
a compact track loader exemplified as the work machine. However,
the work machine according to the embodiment is not limited to the
compact track loader, and may be another type of a loader work
machine such as a skid steer loader for example. In addition, the
work machine may be other than the loader work machine.
[0045] As shown in FIG. 10 and FIG. 11, the work machine 1 includes
a machine body 2, a cabin 3, an work device 4, and a travel device
5.
[0046] Hereinafter, in explanations of all the embodiments of the
present invention, a forward direction (a direction toward a left
side in FIG. 10) corresponds to a front side of an operator seating
on an operator seat 8 of the work machine 1, a backward direction
(a direction toward a right side in FIG. 10) corresponds to a back
side of the operator, a leftward direction (a direction toward a
front side from the back of FIG. 10) corresponds to a left side of
the operator, and a rightward direction (a direction toward a back
side from the front of FIG. 10) corresponds to a right side of the
operator. In the explanations, a machine width direction
corresponds to a horizontal direction perpendicular to the forward
direction and the backward direction. A machine outward direction
corresponds to a direction from a center portion of the machine
body 2 toward the right and corresponds to a direction from the
center portion of the machine body 2 toward the left.
[0047] In other words, the machine outward direction is equivalent
to the machine width direction and is a direction stepping away
from (separating from) a center of the machine width direction. A
direction opposite to the machine outward direction is referred to
as a machine inward direction. In other words, the machine inward
direction is equivalent to the machine width direction and is a
direction stepping up to (being closed to) the center of the
machine width direction.
[0048] The cabin 3 is mounted on the machine body 2. The cabin 3 is
provided with the operator seta 8. The work device 4 is attached to
the machine body 2. The travel device 5 is disposed on an outer
side of the machine body 2. An prime mover is mounted internally on
a rear portion of the machine body 2.
[0049] The work machine 4 includes a boom 10, a work tool 11, a
lift link 12, a control link 13, a boom cylinder 14, and a bucket
cylinder 15.
[0050] The booms 10 are arranged to the right of the cabin 3 and to
the left of the cabin 3, and are capable of swinging upward and
downward. The work tool 11 is a bucket, for example. The bucket 11
is disposed on the tip end portions (the front end portions) of the
booms 10, and is capable of swinging upward and downward.
[0051] The lift link 12 and the control link 13 supports the base
portions (the rear portions) of the booms 10, and thus the booms 10
are capable of swinging upward and downward.
[0052] The boom cylinder 14 is stretched and shortened to move the
booms 10 upward and downward. The bucket cylinder 15 is stretched
and shortened to swing the bucket 11.
[0053] A front portion of the boom 10 arranged to the left is
connected by a deformed connection pipe to a front portion of the
boom 10 arranged to the right. A base portion (a rear portion) of
the boom 10 arranged to the left is connected by a cylindrical
connection pipe to a base portion (a rear portion) of the boom 10
arranged to the right.
[0054] The lift links 12, the control links 13, and the boom
cylinders 14 are arranged to the left of the machine body 2 and to
the right of the machine body 2, corresponding to the boom 10
disposed on the left and the boom 10 disposed on the right.
[0055] The lift links 12 are disposed on the rear portions of the
base portions of the booms 10, and extend in a vertical direction.
The upper portions (one end sides) of the lift links 12 are
pivotally supported by pivotal supports shafts 16 (first pivotal
support shafts), being closer to the rear portions of the base
portions of the booms 10, and are capable of turning about the
lateral axis.
[0056] In addition, the lower portions (the other end sides) of the
lift links 12 are pivotally supported by pivotal supports shafts 17
(second pivotal support shafts), being closer to the rear portions
of the base portions of the booms 10, and are capable of turning
about the lateral axis. The second pivotal support shafts 17 are
arranged below the first pivotal support shafts 16.
[0057] The upper portions of the boom cylinders 14 are pivotally
supported by pivotal support shafts 18 (third pivotal support
shafts), and are capable of turning about the lateral axis. The
third pivotal support shafts 18 are disposed on the base portions
of the booms 10 and specifically on the front portions of the base
portions.
[0058] The lower portions of the boom cylinder 14 are pivotally
supported by pivotal support shafts 19 (fourth pivotal support
shafts), and are capable of turning about the lateral axis. The
fourth pivotal support shafts 19 are disposed below the third
pivotal support shafts 18, being closer to the lower portion of the
rear portion of the machine body 2.
[0059] The control links 13 are arranged in front of the lift links
12. One ends of the control links 13 are pivotally supported by
pivotal supports shafts 20 (fifth pivotal supports shafts), and are
capable of turning about the lateral axis. The fifth pivotal
support shafts 20 are disposed on the machine body 2 and
specifically on corresponding positions in front of the lift links
12.
[0060] The other ends of the control links 13 are pivotally
supported by pivotal supports shafts 21 (sixth pivotal supports
shafts), and are capable of turning about the lateral axis. The
sixth pivotal support shafts 21 are disposed on the booms 10 in
front of the second pivotal support shafts 17 and above the second
pivotal support shafts 17.
[0061] When the boom cylinder 14 is stretched and shortened, the
booms 10 swing upward and downward about the first pivotal support
shafts 16 with the base portions of the booms 10 supported by the
lift links 12 and the control links 13, and thus the tip end
portions of the booms 10 move upward and downward.
[0062] The control links 13 swing upward and downward about the
fifth pivotal support shafts 20 in accordance with the upward
swinging and the downward swinging of the booms 10. The lift links
12 swing forward and backward about the second pivotal support
shafts 17 in accordance with the upward swinging and the downward
swinging of the control links 13.
[0063] The front portions of the booms 10 are capable of attaching
other work tools instead of the bucket 11. The following
attachments (auxiliary attachments) are exemplified as the other
work tools; for example, a hydraulic crusher, a hydraulic breaker,
an angle broom, an earth auger, a pallet fork, a sweeper, a mower,
a snow blower, and the like.
[0064] A connection member 50 is disposed on the front portion of
the boom 10 disposed on the left. The connection member 50 is a
device for connecting a hydraulic device of an auxiliary attachment
to a first tube member pipe such as a pipe disposed on the boom
10.
[0065] Specifically, the first tube member is capable of being
connected to one end of the connection member 50, and a second tube
member is capable of being connected to the other end of the
connection member 50, the second tube member being connected to the
hydraulic device of the auxiliary attachment. In this manner, an
operation fluid flowing in the first tube member is supplied to the
hydraulic device through the second tube member.
[0066] The bucket cylinders 15 are arranged on portions close to
the front portions of the booms 10. The bucket cylinders 15 are
stretched and shortened to swing the bucket 11.
[0067] Each of the travel device 5 disposed on the left and the
travel device 5 disposed on the right employs a travel device of a
crawler type (including a semi-crawler type) in the embodiment.
Each of the travel devices 5 may employ a travel device of a wheel
type having the front wheels and the rear wheels.
[0068] The hydraulic system for the work machine according to the
embodiment will be explained below.
[0069] As shown in FIG. 1, a hydraulic system for travel is a
system for driving the travel device 5. The travel device 5
includes a left travel motor device 31L (a first travel motor
device), a right travel motor device 31R (a second travel motor
device), and a hydraulic device 34. The hydraulic system for travel
includes a prime mover 32, a direction switch valve 33, and a first
hydraulic pump P1.
[0070] The prime mover 32 is constituted of an electric motor, an
engine, or the like. In the embodiment, the prime mover 32 is the
engine. The first hydraulic pump P1 is a pump configured to be
driven by a driving force of the prime mover 32. The first
hydraulic pump P1 is constituted of a constant displacement gear
pump.
[0071] The first hydraulic pump P1 is configured to output the
operation fluid stored in the tank 22. In particular, the first
hydraulic pump P1 outputs the operation fluid mainly used for the
control.
[0072] For convenience of the explanation, the tank 22 for storing
the operation fluid may be referred to as an operation fluid tank.
In addition, of the operation fluid outputted from the first
hydraulic pump P1, the operation fluid used for the control is
referred to as a pilot fluid, and a pressure of the pilot fluid is
referred to as a pilot pressure.
[0073] An output fluid tube (an output fluid path) 40 is disposed
on an output side of the first hydraulic pump P1, the output fluid
tube 40 being configured to supply the operation fluid (the pilot
fluid). The output fluid tube (a first fluid tube) 40 is provided
with a filter 35, the direction switch valve 33, the first travel
motor device 31L, and the second travel motor device 31R.
[0074] A charge fluid tube 41 is arranged between the filter 35 and
the direction switch valve 33, the charge fluid tube 41 being
branched from the output fluid tube 40. The charge fluid tube 41
reaches the hydraulic device 34.
[0075] The direction switch valve 33 is an electromagnetic valve
configured to change revolutions of the first travel motor device
31L and the second travel motor device 31R. The direction switch
valve 33 is constituted of a two-position switch valve being
switched to a first position 33a and to a second position 33b by
magnetization. The direction switch valve 33 is switched by an
operation member and the like not shown in the drawings.
[0076] The first travel motor device 31L is a motor configured to
transmit a motive power to a drive shaft of the travel device 5,
the travel device 5 being arranged to the left of the machine body
2. The second travel motor device 31R is a motor configured to
transmit a motive power to a drive shaft of the travel device 5,
the travel device 5 being arranged to the right of the machine body
2.
[0077] The first travel motor device 31L includes an HST motor (a
travel motor) 36, a swash-plate switch cylinder 37, and a travel
control valve (a hydraulic switch valve) 38. The HST motor 36 is a
variable displacement axial motor having a swash plate, and is a
motor capable of changing a vehicle speed (revolution) to a first
speed and to a second speed. In other words, the HST motor 36 is a
motor capable of changing a thrust power of the work machine 1.
[0078] The swash-plate switch cylinder 37 is a cylinder configured
to be stretched and shortened to change an angle of the swash plate
of the HST motor 36. The travel control valve 38 is a valve for
stretching and shortening the swash-plate switch cylinder 37 to one
side and to the other side, that is, the travel control valve 38 is
constituted of a two-position switch valve configured to be
switched to a first position 38a and to a second position 38b.
[0079] The travel control valve 38 is switched by the direction
switch valve 33 that is connected to the travel control valve 38
and arranged on an upper stream of the travel control valve 38.
[0080] As described above, when the operation member is operated to
switch the direction switch valve 33 to the first position 33a, the
first travel motor 31L releases the pilot fluid in a section
between the direction switch valve 33 and the travel control valve
38, and thus the travel control valve 38 is switched to the first
position 38a. As the result, the swash-plate switch cylinder 37 is
shortened, and thus the HST motor 36 is set to the first speed.
[0081] In addition, when the operation member is operated to switch
the direction switch valve 33 to the second position 33b, the pilot
fluid is supplied to the travel control valve 38 through the
direction switch valve 33, and thus the travel control valve 38 is
switched to the second position 38b. As the result, the swash-plate
switch cylinder 37 is stretched, and thus the HST motor 36 is set
to the second speed.
[0082] Meanwhile, the second travel motor device 31R is operated in
the manner similar to the manner of the first travel motor device
31L. The configurations and movements of the second travel motor
device 31R is similar to the configurations and movements of the
first travel motor device 31L. Thus, the explanation of the second
travel motor device 31R will be omitted.
[0083] The hydraulic device 34 is a device configured to drive the
first travel motor device 31L and the second travel motor device
31R. The hydraulic device 34 includes a drive circuit (a left drive
circuit) 34L and a drive circuit (a right drive circuit) 34R. The
drive circuit 34L is configured to drive the first travel motor
device 31L. The drive circuit 34R is configured to drive the second
travel motor device 31R.
[0084] The drive circuit 34L includes an HST pump (a travel pump)
53L, a speed-changing fluid tube (a speed-changing fluid path) 57h,
a speed-changing fluid tube (a speed-changing fluid path) 57i, and
a second charging fluid tube (a second charging fluid path) 57j.
The drive circuit 34R includes an HST pump (a travel pump) 53R, the
speed-changing fluid tube 57h, the speed-changing fluid tube 57i,
and the second charging fluid tube 57j.
[0085] The speed-changing fluid tubes 57h and 57i are fluid tubes
(fluid paths) connecting the HST pumps 53L and 53R to the HST motor
36.
[0086] The second charging fluid tube 57j is a fluid tube (a fluid
path) connected to the speed-changing fluid tubes 57h and 57i, and
is configured to charge the operation fluid from the first
hydraulic pump P1 to the speed-changing fluid tubes 57h and
57i.
[0087] Each of the HST pumps 53L and 53R is the variable
displacement axial pump having a swash plate. The variable
displacement axial pump is configured to be driven by a motive
power of the prime mover 32. Each of the HST pumps 53L and 53R
includes a forward-movement pressure-receiving portion 53a (a
pressure-receiving portion 53a) and a backward-movement
pressure-receiving portion 53b (a pressure-receiving portion 53b).
The pilot pressure is applied to the forward-movement
pressure-receiving portion 53a and the backward-movement
pressure-receiving portion 53b. An angle of the swash plate is
changed by the pilot pressure applied to the pressure-receiving
portion 53a and the pressure-receiving portion 53b.
[0088] When the angle of the swash plate is changed, the changing
changes the outputs (output amounts of the operation fluid) of the
HST pumps 53L and 53R and changes the directions of the outputs of
the operation fluid.
[0089] An operation device 47 changes the outputs of the HST pumps
53L and 53R and the directions of the outputs of the operation
fluid. The operation device 47 is arranged around the operator seat
8. The operation device 47 includes an operation member 54
swingably supported and a plurality of pilot valves (operation
valves) 55.
[0090] As shown in FIG. 1, the operation member 54 is an operation
lever supported by the operation valve 55 and configured to be
swung in the rightward and leftward directions (the machine width
direction) or in the forward and backward directions. That is, the
operation member 54 is configured to be moved rightward and
leftward from a neutral position N that is a home position, and is
configured to be moved forward and backward from the neutral
position N.
[0091] In other words, the operation member 54 is configured to
move at least in four directions from the home position, the
neutral position N. For convenience of the explanation, the
bi-direction extending forward and backward, that is, corresponding
to the forward direction and the backward direction is referred to
as a first direction. In addition, the bi-direction extending
rightward and leftward, that is, corresponding to the lateral
direction (the machine width direction) is referred to as a second
direction.
[0092] In addition, the plurality of operation valves 55 are
commonly operated by the operation member 54 solely. The plurality
of operation valves 55 are activated in accordance with the
swinging of the operation member 54. The output fluid tube 40 is
connected to the plurality of operation valves 55, and thereby the
operation fluid (the pilot fluid) is supplied from the first
hydraulic pump P1 through the output fluid tube 40. The plurality
of operation valves 55 include an operation valve 55A, an operation
valve 55B, an operation valve 55C, and an operation valve 55D.
[0093] When the operation lever 54 is swung forward (in one
direction) in the forward and backward directions (the first
direction), that is, the operation lever 54 is operated in a
forward operation, the operation valve 55A changes a pressure of
the operation fluid in accordance with an operation amount (the
operation) of the forward operation, the operation fluid being
outputted from the operation valve 55A.
[0094] When the operation lever 54 is swung backward (in the other
direction) in the forward and backward directions (the first
direction), that is, the operation lever 54 is operated in a
backward operation, the operation valve 55B changes the pressure of
the operation fluid in accordance with an operation amount (the
operation) of the forward operation, the operation fluid being
outputted from the operation valve 55B.
[0095] When the operation lever 54 is swung rightward (in one
direction) in the lateral direction (the second direction), that
is, the operation lever 54 is operated in a rightward operation,
the operation valve 55C changes the pressure of the operation fluid
in accordance with an operation amount (the operation) of the
rightward operation, the operation fluid being outputted from the
operation valve 55C.
[0096] When the operation lever 54 is swung leftward (in the other
direction) in the lateral direction (the second direction), that
is, the operation lever 54 is operated in a leftward operation, the
operation valve 55D changes the pressure of the operation fluid in
accordance with an operation amount (the operation) of the leftward
operation, the operation fluid being outputted from the operation
valve 55D.
[0097] The plurality of operation valves 55 are connected to the
hydraulic device 34 for travel (the travel pump 53L and the travel
pump 53R) by a travel fluid tube (a second fluid tube) 45. In other
words, the travel pumps 53L and 53R are hydraulic devices
configured to be activated by the operation fluid outputted from
the operation valves 55 (the operation valve 55A, the operation
valve 55B, the operation valve 55C, and the operation valve
55D).
[0098] The travel fluid tube 45 includes a first travel fluid tube
45a, a second travel fluid tube 45b, a third travel fluid tube 45c,
a fourth travel fluid tube 45d, and a fifth travel fluid tube
45e.
[0099] The first travel fluid tube 45a is a fluid tube (a fluid
path) connected to the forward-movement pressure-receiving portion
53a of the travel pump 53L.
[0100] The second travel fluid tube 45b is a fluid tube (a fluid
path) connected to the backward-movement pressure-receiving portion
53b of the travel pump 53L.
[0101] The third travel fluid tube 45c is a fluid tube (a fluid
path) connected to the forward-movement pressure-receiving portion
53a of the travel pump 53R.
[0102] The fourth travel fluid tube 45d is a fluid tube (a fluid
path) connected to the backward-movement pressure-receiving portion
53b of the travel pump 53R.
[0103] The fifth travel fluid tube 45e is a fluid tube (a fluid
path) connecting the operation valves 55, the first travel fluid
tube 45a, the second travel fluid tube 45b, the third travel fluid
tube 45c, and the fourth travel fluid tube 45d to each other.
[0104] The fifth travel fluid tube 45e includes a bridge portion
45e1 and a connection tube (a connection path) 45e2. The bridge
portion 45e1 has a plurality of shuttle valves 46. The connection
tube 45e2 connects the operation valves 55 to a confluence portion
of the bridge portion 45e1.
[0105] When the operation lever 54 is swung forward (in a direction
represented by an arrowed line A1 in FIG. 1), the operation valve
55A is operated to output the pilot pressure from the operation
valve 55A. The pilot pressure is applied to the pressure-receiving
portion 53a of the travel pump 53L through the first travel fluid
tube 45a and to the pressure-receiving portion 53a of the travel
pump 53R through the third travel fluid tube 45c.
[0106] In this manner, output shafts of the travel motors 36
normally turn (turn forward) at a speed proportional to a swinging
amount (a swinging extent) of the operation lever 54, and thus the
work machine 1 travels straight forward.
[0107] In addition, when the operation lever 54 is swung backward
(in a direction represented by an arrowed line A2 in FIG. 1), the
operation valve 55B is operated to output the pilot pressure from
the operation valve 55B. The pilot pressure is applied to the
pressure-receiving portion 53b of the travel pump 53L through the
second travel fluid tube 45b and to the pressure-receiving portion
53b of the travel pump 53R through the fourth travel fluid tube
45d.
[0108] In this manner, the output shafts of the travel motors 36
reversely turn (turn backward) at a speed proportional to the
swinging amount (the swinging extent) of the operation lever 54,
and thus the work machine 1 travels straight backward.
[0109] In addition, when the operation lever 54 is swung rightward
(in a direction represented by an arrowed line A3 in FIG. 1), the
operation valve 55C is operated to output the pilot pressure from
the operation valve 55C. The pilot pressure is applied to the
pressure-receiving portion 53a of the travel pump 53L through the
first travel fluid tube 45a and to the pressure-receiving portion
53b of the travel pump 53R through the fourth travel fluid tube
45d.
[0110] In this manner, the output shaft of the travel motor 36
arranged to the left normally turns, the output shaft of the travel
motor 36 arranged to the right reversely turns, and thus the work
machine 1 turns rightward.
[0111] In addition, when the operation lever 54 is swung leftward
(in a direction represented by an arrowed line A4 in FIG. 1), the
operation valve 55D is operated to output the pilot pressure from
the operation valve 55C. The pilot pressure is applied to the
pressure-receiving portion 53a of the travel pump 53R through the
third travel fluid tube 45c and to the pressure-receiving portion
53b of the travel pump 53L through the second travel fluid tube
45b.
[0112] In this manner, the output shaft of the travel motor 36
arranged to the left reversely turns, the output shaft of the
travel motor 36 arranged to the right normally turns, and thus the
work machine 1 turns leftward.
[0113] In addition, when the operation lever 54 is swung in a
diagonal direction, turning directions and turning speeds of the
output shafts of the travel motor 36 arranged to the left side and
the travel motor 36 arranged to the right side are determined by a
differential pressure between the pilot pressure applied to the
pressure-receiving portion 53a and the pilot pressure applied to
the pressure-receiving portion 53b, and thus the work machine 1
turns rightward or leftward traveling forward or backward.
[0114] That is, when the operation lever 54 is swung (operated)
forward and diagonally-leftward, the work machine 1 turns leftward
traveling forward at a speed corresponding to a swinging angle of
the operation lever 54. When the operation lever 54 is swung
(operated) forward and diagonally-rightward, the work machine 1
turns rightward traveling forward at a speed corresponding to a
swinging angle of the operation lever 54. When the operation lever
54 is swung (operated) backward and diagonally-leftward, the work
machine 1 turns leftward traveling backward at a speed
corresponding to a swinging angle of the operation lever 54. When
the operation lever 54 is swung (operated) backward and
diagonally-rightward, the work machine 1 turns rightward traveling
backward at a speed corresponding to a swinging angle of the
operation lever 54.
[0115] As shown in FIG. 2, the hydraulic system for work is a
system configured to operate the booms 10. the bucket 11, an
auxiliary attachment, and the like. The hydraulic system for work
includes a plurality of control valves 56 and an operation
hydraulic pump 8a second hydraulic pump) P2.
[0116] The second hydraulic pump P2 is a pump arranged on a
position different from the position of the first hydraulic pump
P1, and is constituted of a constant displacement gear pump. The
second hydraulic pump P2 is configured to output the operation
fluid stored in the operation fluid tank 22. In particular, the
second hydraulic pump P2 outputs the operation fluid mainly used
for operating the hydraulic actuators.
[0117] A main fluid tube (a fluid path) 39 is disposed on an output
side of the second hydraulic pump P2. The plurality of control
valves 56 are connected to the main fluid tube 39. The control
valve 56 is a valve configured to be switched by the pilot pressure
of the pilot fluid, and thereby the control valve 56 is configured
to change a direction of supplying of the operation fluid.
[0118] As shown in FIG. 2, the plurality of control valves 56
includes a first control valve 56A, a second control valve 56B, and
a third control valve 56C.
[0119] The first control valve 56A is a valve configured to control
the hydraulic cylinder (the boom cylinder) 14 for controlling the
boom.
[0120] The second control valve 56B is a valve configured to
control the hydraulic cylinder (the bucket cylinder) 15 for
controlling the bucket.
[0121] The third control valve 56C is a valve configured to control
the auxiliary hydraulic actuators attached to the auxiliary
attachments such as the hydraulic crusher, the hydraulic breaker,
the angle broom, the earth auger, the pallet fork, the sweeper, the
mower, the snow blower.
[0122] Each of the first control valve 56A and the second control
valve 56B is constituted of a three-position switch valve having a
direct-acting spool that is configured to be driven by the pilot
pressure. Each of the first control valve 56A and the second
control valve 56B is switched by the pilot pressure to a neutral
position, to a first position different from the neural position,
and to a second position different from the neutral position and
the first position.
[0123] The boom cylinder 14 is connected to the first control valve
56A by a fluid tube. The bucket cylinder 15 is connected to the
second control valve 56B by a fluid tube.
[0124] The boom 10 and the bucket 11 are operated by an operation
device 48 arranged around the operator seat 8. The operation device
48 includes an operation member 58 and a plurality of pilot valves
(operation valves) 59, the operation member 58 being supported
swingably.
[0125] The operation member 58 is an operation lever supported by
the operation valves 59 and configured to be swung in the rightward
and leftward directions (the machine width direction) or in the
forward and backward directions. In addition, the plurality of
operation valves 59 are operated in accordance with the swinging of
the operation member (the operation lever) 58.
[0126] The output fluid tube 40 is connected to the plurality of
operation valves 59, and thus the operation fluid (the pilot fluid)
is supplied from the first hydraulic pump P1 to the operation
valves 59 through the output fluid tube 40.
[0127] The plurality of operation valves 59 include the operation
valve 59A, the operation valve 59B, the operation valve 59C, and
the operation valve 59D.
[0128] When the operation lever 58 is swung forward (a forward
operation is performed), the operation valve 59A changes the
pressure of the operation fluid in accordance with an operation
amount (an operation extent) of the forward operation.
[0129] When the operation lever 58 is swung backward (a backward
operation is performed), the operation valve 59B changes the
pressure of the operation fluid in accordance with an operation
amount (an operation extent) of the backward operation.
[0130] When the operation lever 58 is swung rightward (a rightward
operation is performed), the operation valve 59C changes the
pressure of the operation fluid in accordance with an operation
amount (an operation extent) of the rightward operation.
[0131] When the operation lever 58 is swung leftward (a leftward
operation is performed), the operation valve 59D changes the
pressure of the operation fluid in accordance with an operation
amount (an operation extent) of the leftward operation.
[0132] The plurality of operation valves 59 (the operation valve
59A, the operation valve 59B, the operation valve 59C, and the
operation valve 59D) are connected to a working fluid tube 43. The
working fluid tube 43 includes a first working fluid tube 43a, a
second working fluid tube 43b, a third working fluid tube 43c, and
a fourth working fluid tube 43d.
[0133] The first working fluid tube 43a is a fluid tube connected
to the first control valve 56A and the operation valve 59A.
[0134] The second working fluid tube 43b is a fluid tube connected
to the first control valve 56A and the operation valve 59B.
[0135] The third working fluid tube 43c is a fluid tube connected
to the second control valve 56B and the operation valve 59C.
[0136] The fourth working fluid tube 43d is a fluid tube connected
to the second control valve 56B and the operation valve 59D.
[0137] When the operation lever 58 is tilted forward, the pilot
valve (operation valve) 59A for downward movement is operated to
set the pilot pressure of the pilot fluid that is to be outputted
from the downward movement operation valve 59A. The pilot pressure
is applied to the pressure-receiving portion of the first control
valve 56A, and thereby shortening the boom cylinder 14 to move the
boom 10 downward.
[0138] When the operation lever 58 is tilted backward, the pilot
valve (operation valve) 59B for upward movement is operated to set
the pilot pressure of the pilot fluid that is to be outputted from
the upward movement operation valve 59B. The pilot pressure is
applied to the pressure-receiving portion of the first control
valve 56A, and thereby stretching the boom cylinder 14 to move the
boom 10 upward.
[0139] When the operation lever 58 is tilted rightward, the pilot
valve (operation valve) 59C for bucket dumping is operated to set
the pilot pressure of the pilot fluid that is to be outputted from
the bucket dumping operation valve 59C. The pilot pressure is
applied to the pressure-receiving portion of the second control
valve 56B, and thereby stretching the bucket cylinder 15 to perform
the dumping movement of the bucket 11.
[0140] When the operation lever 58 is tilted leftward, the pilot
valve (operation valve) 59D for bucket shoveling is operated to set
the pilot pressure of the pilot fluid that is to be outputted from
the bucket dumping operation valve 59D. The pilot pressure is
applied to the pressure-receiving portion of the second control
valve 56B, and thereby shortening the bucket cylinder 15 to perform
the shoveling movement of the bucket 11.
[0141] The third control valve 56C is constituted of a
three-position switch valve having a direct-acting spool that is
configured to be driven by the pilot pressure. The third control
valve 56C is switched by the pilot pressure to a first position
62a, to a second position 62b, and to a third position (a neutral
position) 62c.
[0142] That is, the third control valve 56C is switched to the
first position 62a, to the second position 62b, and to the third
position 62C, and thereby controls a direction, a flow rate, and a
pressure of the operation fluid flowing to the auxiliary hydraulic
actuator.
[0143] A supply-discharge fluid tube (a supply-discharge fluid
path) 83 is connected to the third control valve 56C. One end of
the supply-discharge (supply-drain) fluid tube 83 is connected to a
supply-discharge port of the third control valve 56C. An
intermediate portion of the supply-discharge fluid tube 83 is
connected to the connection member 50. The other end of the
supply-discharge fluid tube 83 is connected to the auxiliary
hydraulic actuator. The supply-discharge fluid tube 83 is
constituted of the first tube member and the second tube member
described above.
[0144] In particular, the supply-discharge fluid tube 83 includes a
first supply-discharge (supply-drain) fluid tube 83a that connects
a first supply-discharge (supply-drain) port of the third control
valve 56C to a first port of the connection member 50. In addition,
the supply-discharge fluid tube 83 includes a second
supply-discharge (supply-drain) fluid tube 83b that connects a
second supply-discharge port of the third control valve 56C to a
second port of the connection member 50.
[0145] That is, the operation of the third control valve 56C allows
to supply the operation fluid from the third control valve 56C
toward the first supply-discharge fluid tube 83a, and to supply the
operation fluid from the third control valve 56C toward the second
supply-discharge fluid tube 83b.
[0146] The third control valve 56C is operated by a plurality of
proportional valves 60. Each of the proportional valves 60 is
constituted of an electromagnetic valve configured to change an
aperture of the proportional valve by being magnetized. The
plurality of proportional valves 60 include a first proportional
valve 60A and a second proportional valve 60B.
[0147] An output fluid tube (an output fluid path) 40 is connected
to the first proportional valve 60A and the second proportional
valve 60B. The proportional valves 60 (the first proportional valve
60A and the second proportional valve 60B) and the third control
valve 56C are connected to each other by a fluid tube (a fluid
path) 86.
[0148] The fluid tube 86 is a fluid for supplying the pilot fluid
to the third control valve 56C through the proportional valves 60
(the first proportional valve 60A and the second proportional valve
60B). The fluid tube 86 is constituted of a tube member such as a
steel tube, a pipe, and a hose.
[0149] The fluid tube 86 includes a first control fluid tube 86a
and a second control fluid tube 86b. The first control fluid tube a
connects the first proportional valve 60A to the pressure-receiving
portion 61a of the third control valve 56C. The second control
fluid tube 86b connects the second proportional valve 60B to the
pressure-receiving portion 61b of the third control valve 56C.
[0150] Thus, the pilot fluid is applied to the pressure-receiving
portion 61a of the third control valve 56C through the first
control fluid tube 86a when the first proportional valve 60A is
opened, and then the pilot pressure given (applied) to the
pressure-receiving portion 61a on the basis of the aperture of the
first proportional valve 60A.
[0151] When the pilot pressure applied to the pressure-receiving
portion 61a is equal to or more than a predetermined pressure, the
third control valve 56C is switched from the third position (the
neutral position) 62c to the first position 62a by movement of the
spool.
[0152] In addition, the pilot fluid is applied to the
pressure-receiving portion 61b of the third control valve 56C
through the second control fluid tube 86b when the second
proportional valve 60B is opened, and then the pilot pressure given
(applied) to the pressure-receiving portion 61b on the basis of the
aperture of the second proportional valve 60B.
[0153] When the pilot pressure applied to the pressure-receiving
portion 61b is equal to or more than a predetermined pressure, the
third control valve 56C is switched from the third position (the
neutral position) 62c to the second position 62b by movement of the
spool.
[0154] The control device (the first control device) 90 magnetizes
the proportional valves 60 (the first proportional valve 60A and
the second proportional valve 60B). The control device 90 is
constituted of a CPU and the like. A switch 96 is connected to the
control device 90, the switch 96 being arranged around the operator
seat 8. The control device (the first control device) 90 may be
referred to as the controller (the first controller) 90
[0155] The switch 96 is constituted of a seesaw switch configured
to be swung, a slide switch configured to be slid, or a push switch
configured to be pushed. An operation of the switch 96 is inputted
to the control device 90.
[0156] The operation of the switch 96 opens and closes the first
proportional valve 60A or the second proportional valve 60B. In
this manner, the auxiliary actuator is operated under the control
of the control device 90.
[0157] As shown in FIG. 1, the work machine 1 includes a control
device (a controller) 92 in addition to the control device 90, the
control device 92 being configured to control the prime mover 32.
For example, in a case where the prime mover 32 is an engine, the
control device 92 is an engine control device (an engine
controller).
[0158] For convenience of the explanation, the explanation will be
made assuming that the prime mover 32 is an engine. In the
following explanations, the control device (controller) 90 will be
referred to as "a first control device (first controller) 90", and
the control device (controller) 92 will be referred to as "a second
control device (second controller) 92".
[0159] An ordering member 93 is connected to the second control
device 92. The ordering member 93 is configured to order a target
engine revolution speed (referred to as a target revolution speed
of engine). The ordering member 93 includes a pedal portion 93a and
a sensor 93b. The sensor 93b detects an operation amount (an
operation extent) of the pedal portion 93a.
[0160] The pedal portion 93a is constituted of an acceleration
lever supported swingably or an acceleration pedal supported
swingably. The operation amount (operation extent) detected by the
sensor 93b is inputted to the second control device 92. The
operation amount (operation extent) detected by the sensor 93b is
the target revolution speed of engine.
[0161] A sensor (measurement device) 94 is connected to the second
control device 92. The sensor 94 is configured to detect an actual
engine revolution speed (referred to as an actual revolution speed
of the engine).
[0162] The second control device 91 provides a general engine
control, and outputs the control signals representing a fuel
injection amount, an injection timing, and a fuel injection rate to
an injector, for example. In addition, the second control device 92
outputs the control signal representing the fuel injection pressure
to a supply pump and to the common rail.
[0163] That is, the second control device controls the injector,
the supply pump, and the common rail such that the actual
revolution speed of the engine satisfies the target revolution
speed of the engine.
[0164] The first control device 90 performs a control (an
anti-stall control) to prevent an engine stall in addition to the
control to the proportional valves 60 and the like. in particular,
an operation valve (a second operation valve 44) is connected to
the first control device 90, the operation valve 44 being disposed
on the output fluid tube 40.
[0165] In the embodiment, the operation valve 44 is constituted of
an electromagnetic valve (a proportional valve). The first control
device 90 changes an aperture of the proportional valve 44 on the
basis of a drop amount of the engine that is a difference between
the target revolution speed of the engine and the actual revolution
speed of the engine, thereby preventing the engine stall.
[0166] The first control device 90 is capable of obtaining the
actual revolution speed of the engine and the target revolution
speed of the engine. Meanwhile, the operation valve 44 may be
constituted of a switch valve or may be constituted of a throttle
portion.
[0167] FIG. 3 is a view illustrating a relation between the engine
revolution sped, a travel primary pressure, the control line L1,
and the control line L2.
[0168] The travel primary pressure is a pressure (the pilot
pressure) of the operation fluid in a section from the proportional
valve 44 to the operation valves 55 (the operation valve 55A, the
operation valve 55B, the operation valve 55C, and the operation
valve 55D). That is, the travel primary pressure is a primary
pressure of the operation fluid flowing into the operation valves
55 disposed to the operation lever 54.
[0169] The control line L1 shows a relation between the travel
primary pressure and the engine revolution speed of a case where
the drop amount is less than a predetermined amount.
[0170] The control line L2 shows a relation between the travel
primary pressure and the engine revolution speed of a case where
the drop amount is equal to or more than the predetermined
amount.
[0171] The first control device 90 adjusts the aperture of the
proportional valve 44 in the case where the drop amount is less
than the predetermined amount such that the relation between the
actual revolution speed of the engine and the travel primary
pressure corresponds to the control line L1. In addition, the first
control device 90 adjusts the aperture of the proportional valve 44
in the case where the drop amount is equal to or more than the
predetermined amount such that the relation between the actual
revolution speed of the engine and the travel primary pressure
corresponds to the control line L2.
[0172] On the control line L2, the travel primary pressure to a
predetermined engine revolution speed is lower than the travel
primary pressure of the control line L1. That is, at the identical
engine revolution speed, the travel primary pressure of the control
line L2 is lower than the travel primary pressure of the control
line L1.
[0173] In this manner, the pressure (the pilot pressure) of the
operation fluid flowing into the operation valves 55 is suppressed
to be low under the control based on the control line L2. As the
result, the swash plate angle of the HST pump 66 of the HST pump
(the travel pump) 53 is adjusted, and thereby a load applied to the
engine 32 is reduced to prevent the engine stall of the engine
32.
[0174] Meanwhile, the control line L2 is shown singularly in FIG.
3. However, a plurality of the control lines L2 may be provided.
For example, the control lines L2 may be set for each of the engine
revolution speeds. In addition, the first control device 90 may
have the dada or the control parameters such as the functions
representing the control line L1 and the control line L2.
[0175] Then, the hydraulic system is provided with a circuit
capable of reducing the pressure (performing the pressure
reduction) of the operation fluid in the travel fluid tube (the
second fluid tube) 45. As shown in FIG. 1, a discharge fluid tube
(a drain fluid tube) 71 is connected to the travel fluid tube (the
second fluid tube) 45.
[0176] In particular, the discharge fluid tube 71 includes a first
discharge fluid tube (a first drain fluid tube) 71a, a second
discharge fluid tube (a second drain fluid tube) 71b, a third
discharge fluid tube (a third drain fluid tube) 71c, a fourth
discharge fluid tube (a fourth drain fluid tube) 71d, and a fifth
discharge fluid tube (a fifth drain fluid tube) 71e.
[0177] The first discharge fluid tube 71a is a fluid tube branching
from an intermediated portion of the first travel fluid tube 45a.
The second discharge fluid tube 71b is a fluid tube branching from
an intermediated portion of the second travel fluid tube 45b.
[0178] The third discharge fluid tube 71c is a fluid tube branching
from an intermediated portion of the third travel fluid tube 45c.
The fourth discharge fluid tube 71d is a fluid tube branching from
an intermediated portion of the fourth travel fluid tube 45d.
[0179] The fifth discharge fluid tube 71e is a fluid tube
connecting the first discharge fluid tube 71a, the second discharge
fluid tube 71b, the third discharge fluid tube 71c, and the fourth
discharge fluid tube 71d to each other. The fifth discharge fluid
tube 71e is connected also to the operation fluid tank 22. An
operation valve (a first operation valve) 72 is connected to an
intermediate portion of the fifth discharge fluid tube 71e.
[0180] Check valves 73 are disposed to each of the first discharge
fluid tube 71a, the second discharge fluid tube 71b, the third
discharge fluid tube 71c, and the fourth discharge fluid tube
71d.
[0181] A connecting portion between the second fluid tube 45 (the
first travel fluid tube 45a, the second travel fluid tube 45b, the
third travel fluid tube 45c, and the fourth travel fluid tube 45d)
and the discharge fluid tubes 71 (the first discharge fluid tube
71a, the second discharge fluid tube 71b, the third discharge fluid
tube 71c, and the fourth discharge fluid tube 71d) is referred to
as "a connecting portion C1".
[0182] In that case, the check valve 73 allows the operation fluid
to flow from the connecting portion C1 to the fifth discharge fluid
tube 71e and blocks the operation fluid flowing from the fifth
discharge fluid tube 71e to the connecting portion C1.
[0183] A throttle portion 74 is disposed on the travel fluid tube
(the second fluid tube) 45. The throttle portion 74 is configured
to reduce a flow amount of the operation fluid from the operation
valve 55 to the discharge fluid tube 71. The throttle portion 74
includes a first throttle portion 74a, a second throttle portion
74b, a third throttle portion 74c, and a fourth throttle portion
74d.
[0184] The first throttle portion 74a is a throttle that is
disposed on an upper stream of the connection portion C1 connected
to the first discharge fluid tube 71a (on a side of the operation
valve 55) in the first travel fluid tube 45a.
[0185] The second throttle portion 74b is a throttle that is
disposed on the upper stream of the connection portion C1 connected
to the second discharge fluid tube 71b in the second travel fluid
tube 45b.
[0186] The third throttle portion 74c is a throttle that is
disposed on the upper stream of the connection portion C1 connected
to the third discharge fluid tube 71c in the third travel fluid
tube 45c.
[0187] The fourth throttle portion 74d is a throttle that is
disposed on the upper stream of the connection portion C1 connected
to the fourth discharge fluid tube 71d in the fourth travel fluid
tube 45d.
[0188] The operation valve 72 is a variable relief valve configured
to magnetize a solenoid of the operation valve 72 and thereby to
change a set pressure of the operation valve 72. When the set
pressure of the variable relief valve 72 is set to be lower than a
predetermined pressure (to be lower than the pressure of the
operation fluid in the second fluid tube 45), the variable relief
valve 72 is operated (opened).
[0189] Thus, the operation fluid of the second fluid tube 45 (the
first travel fluid tube 45a, the second travel fluid tube 45b, the
third travel fluid tube 45c, and the fourth travel fluid tube 45d)
can be supplied to the fifth discharge fluid tube 71e and then
discharged (drained) to the operation fluid tank 22 through the
variable relief valve 72.
[0190] On the other hand, when the set pressure of the variable
relief valve 72 is increased (sets the set pressure to be larger
than the pressure of the operation fluid in the second fluid tube
45), the variable relief valve 72 is not operated (still
closed).
[0191] Thus, the operation fluid in the second fluid tube 45 dose
not flow to the fifth discharge fluid tube 71e, and thus the
pressure of the operation fluid in the second fluid tube 45
operates the travel pump 53L and the travel pump 53R.
[0192] The control device 90 changes the set pressure of the
variable relief valve 72. A detection device (a first temperature
sensor or a first measurement detector) 91 is connected to the
control device 90. The detection device 91 is configured to detect
(measure) a temperature of the operation fluid.
[0193] The first detection device 91 detects (measures) a
temperature of the operation fluid in the operation fluid tank 22,
a temperature of the operation fluid outputted from the first
hydraulic pump P1, and the like. For example, the first measurement
device 91 is disposed on a hose or a pipe connected to a suction
port of the first hydraulic pump P1.
[0194] Meanwhile, the first detection device 91 may be disposed in
front of the branching of the first hydraulic pump P1 and the
second hydraulic pump P2 or behind the branching of the first
hydraulic pump P1 and the second hydraulic pump P2. In addition, an
installation site of the first detection device 91 is not limited
to the above-mentioned site.
[0195] In a case where the temperature of the operation fluid (the
fluid temperature) measured by the first measurement device 91 is
equal to or less than a predetermined temperature, the control
device 90 outputs a control signal and the like to reduce the set
pressure of the variable relief valve 72 to be lower than a
predetermined value (reduce the set pressure such that a secondary
pressure is lower than the primary pressure of the operation valve
55), thereby opening the variable relief valve 72.
[0196] For example, in a case where the fluid temperature is equal
to or less than a predetermined temperature and is a low
temperature, the set pressure of the variable relief valve 72 is
set to be minimum. The low temperature corresponds to a temperature
range where a viscosity of the operation fluid is very high, the
operation fluid having a viscosity grade (a dynamic viscosity)
generally used for the work machine, and a range where the pressure
of the operation fluid is increased in the fluid tube. For example,
the pressure of the operation fluid is increased when the fluid
temperature is 0.degree. C. or less, especially when the fluid
temperature is -10.degree. C. or less.
[0197] Meanwhile, the aperture of the operation valve 72 (the
variable relief valve 72) is not limited to the above-mentioned
aperture. For example, in a case where the fluid temperature is
high, the set value of the variable of relief valve 72 may be
increased to make the variable relief valve 72 be closed (fully
closed).
[0198] In this manner, the set pressure of the variable relief
valve 72 is lowered in the case where the fluid temperature
measured by the first measurement device 91 is low, and thus the
operation fluid of the secondary side (the second fluid tube 45) of
the operation valve 55 can be circulated, thereby easily warming up
the operation fluid.
[0199] In addition, the set pressure of the variable relief valve
72 is lowered in the case where the temperature of the operation
fluid is low (the pilot pressure is limited), and thus the movement
of the work machine 1 can be slow down to prevent an error in
operation.
[0200] Meanwhile, a measurement device (sensor) configured to
measure the primary pressure and the secondary pressure of the
operation valve 55 may be provided, and thereby the set pressure of
the variable relief valve 72 may be changed such that "the primary
pressure>the secondary pressure" is satisfied in the case where
the operation fluid is at the low temperature.
[0201] In addition, the control device 90 returns the set pressure
of the variable relief valve 72 to the predetermined set pressure
in a case where the temperature of the operation fluid (the fluid
temperature) measured by the first measurement device 91 is not
equal to or less than the predetermined temperature (the low
temperature).
[0202] Meanwhile, the control device 90 may be provided with a
second measurement device (sensor) 95 that is configured to measure
(detect) a temperature of outside air (an outside temperature). The
control device 90 may change the set pressure of the variable
relief valve 72 on the basis of the temperature of outside air
measured by the second measurement device 95. The outside
temperature is a temperature of a periphery of the work machine 1
or a temperature of a periphery of the devices mounted on the work
machine 1, for example.
[0203] In particular, the variable relief valve 72 is opened in a
case where the temperature of the operation fluid is equal to or
less than a predetermined temperature and the temperature of
outside air measured by the second measurement device 95 is equal
to or less than a predetermined temperature. For example, the set
pressure of the variable relief valve 72 is lowered in a case where
the outside temperature measured by the second measurement device
95 is low equal to or less than the degree below freezing and the
fluid temperature measured by the first measurement device 91 is
low.
[0204] Meanwhile, the operation valve 72 is constituted of the
variable relief valve 72 in the embodiment mentioned above, the
variable relief valve 72 being configured to change the set
pressure. However, the operation valve 72 may be constituted of an
electromagnetic proportional valve (a proportional valve). Also in
that case, the proportional valve 72 is opened in the case where
the temperature (the fluid temperature) of the operation fluid is
equal to or less than the predetermined temperature (low), the
temperature being measured by the first measurement device 91, and
the proportional valve 72 is closed in the case where the fluid
temperature is not equal to or less than the predetermined
temperature.
[0205] In addition, in the case where the second measurement device
95 is provided, the proportional valve 72 is opened in the case
where the temperature of the operation fluid is equal to or less
than the predetermined temperature and the temperature of outside
air measured by the second measurement device 95 is equal to or
less than the predetermined temperature, and is closed in other
cases.
[0206] The control device 90 may control the proportional valve 72
in the similar manner to the variable relief valve 72.
[0207] The hydraulic system according to the embodiment easily
warms up the operation fluid in the fluid tube from the operation
valve for operating a hydraulic device to the hydraulic device. In
addition, the hydraulic system according to the embodiment improves
a responsibility of the anti-stall control, the anti-stall control
preventing the engine stall. Moreover, the hydraulic system
according to the embodiment improves the traveling performance of
the work machine. Furthermore, the hydraulic system according to
the embodiment easily brakes the work machine and releases the
braking.
Second Embodiment
[0208] FIG. 4 is a view illustrating a hydraulic system according
to a second embodiment of the present invention. The hydraulic
system for travel according to the second embodiment can be applied
to the hydraulic system according to the first embodiment described
above. Thus, explanations of configurations similar to the
configurations of the first embodiment will be omitted.
[0209] As shown in FIG. 4, the hydraulic system is provided with a
third fluid tube (a third fluid path) 100 in the output fluid tube
40. The third fluid tube 100 connects the second fluid tube 45 to a
section 40A that is positioned between the plurality of operation
valves 55 and the proportional valve 44.
[0210] The third fluid tube 100 includes a first communication
fluid tube (a first communication fluid path) 101 and a second
communication fluid tube (a second communication fluid path) 102.
The first communication fluid tube 101 is a fluid tube (a fluid
path) connecting an intermediate portion of the first travel fluid
tube 45a to an intermediate portion of the second travel fluid tube
45b.
[0211] Meanwhile, the first communication fluid tube 101 may be a
fluid tube connecting an intermediate portion of the third travel
fluid tube 45b to the fourth travel fluid tube 45d.
[0212] The second communication fluid tube 102 is a fluid tube (a
fluid path) connecting an intermediate portion of the first
communication fluid tube 101 to the section 40A of the output fluid
tube 40. Hereinafter, a connecting portion connecting the first
travel fluid tube 45a to the first communication fluid tube 101 is
referred to as "a connecting portion C2", a connecting portion
connecting the second travel fluid tube 45b to the first
communication fluid tube 101 is referred to as "a connecting
portion C3", and a connecting portion connecting the first
communication fluid tube 101 to the second communication fluid tube
102 is referred to as "a connecting portion C4".
[0213] In that case, check valves 103a and 103b are disposed on
each of a section between the connecting portion C2 and the
connecting portion C4 in the first communication fluid tube 101 and
a section between the connecting portion C3 and the connecting
portion C4 in the first communication fluid tube 101.
[0214] The check valve 103a allows the operation fluid to flow from
the first travel fluid tube 45a to the second communication fluid
tube 102 and blocks the flowing of the operation fluid flowing from
the second communication fluid tube 102 to the first travel fluid
tube 45a. The check valve 103b allows the operation fluid to flow
from the second travel fluid tube 45b to the second communication
fluid tube 102 and blocks the flowing of the operation fluid
flowing from the second communication fluid tube 102 to the second
travel fluid tube 45b.
[0215] That is, each of the check valves 103a and 103b allows the
operation fluid to flow from the second fluid tube 45 to the output
fluid tube 40 (the section 40A) and blocks the flowing of the
operation fluid flowing from the output fluid tube 40 (the section
40A) to the second fluid tube 45.
[0216] In addition, the travel fluid tube (the second fluid tube)
45 is provided with a throttle portion 104 that is configured to
reduce a flow rate of the operation fluid flowing from the
operation valve 55 to the third fluid tube 100 (the first
communication fluid tube 101). The throttle portion 104 includes a
first throttle portion 104a and a second throttle portion 104b.
[0217] The first throttle portion 104a is a throttle disposed on an
upper stream (on a side of the operation valve 55) of the
connecting portion C2 of the first travel fluid tube 45a. The
second throttle portion 104b is a throttle disposed on an upper
stream of the connecting portion C2 of the second travel fluid tube
45b.
[0218] In the case where the anti-stall control is performed, the
aperture of the operation valve 44 is set on the basis of the drop
amount, and thereby the pressure of the secondary side of the
operation valve 55 (the pressure of the operation fluid in the
second fluid tube 45) is reduced.
[0219] In a case where a path (the second fluid tube 45) from the
operation valve 55 to the travel pumps 53L and 53R is long or a
throttle portion is disposed on the second fluid tube 45, a time
for the reduction of the pressure of the secondary side of the
operation valve 55 (the pressure of the operation fluid in the
second fluid tube 45) is long, and thus resulting in a response
delay.
[0220] The hydraulic system for the work machine described above
includes the third fluid tube 100 and the check valve 103. The
third fluid tube 100 connects the second fluid tube 45 to the
section 40A positioned between the operation valve 55 and the
proportional valve 44. The check valve 103 is disposed on the third
fluid tube 100. Thus, the operation fluid in the second fluid tube
45 can be discharged (drained) through the third fluid tube 100 and
the proportional valve 44 in a case where the revolution speed of
the engine widely drops, that is, in a case where the drop amount
is large.
[0221] In this manner, the response delay mentioned above can be
prevented. That is, in the case where the revolution speed of the
engine widely drops, the pressure of the operation fluid can be
rapidly reduced in the second fluid tube 45, and thereby the engine
stall is prevented.
[0222] In addition, even in a case where the throttle portion 104
is disposed between the operation valve 55 and a portion connected
to the third fluid tube 100 on the second fluid tube 45, the
pressure of the operation fluid can be rapidly reduced in the
second fluid tube 45 as described above, and thereby the engine
stall is prevented.
[0223] The hydraulic system according to the embodiment easily
warms up the operation fluid in the fluid tube from the operation
valve for operating a hydraulic device to the hydraulic device. In
addition, the hydraulic system according to the embodiment improves
a responsibility of the anti-stall control, the anti-stall control
preventing the engine stall. Moreover, the hydraulic system
according to the embodiment improves the traveling performance of
the work machine. Furthermore, the hydraulic system according to
the embodiment easily brakes the work machine and releases the
braking.
Third Embodiment
[0224] FIG. 5 is a view illustrating a hydraulic system according
to a third embodiment of the present invention. The hydraulic
system for travel according to the third embodiment can be applied
to the hydraulic systems according to the first embodiment and the
second embodiment described above. Thus, explanations of
configurations similar to the configurations of the first
embodiment and the second embodiment will be omitted.
[0225] As shown in FIG. 5, the hydraulic system according to the
embodiment includes a pressure changing portion (a pressure
changer) 110. The pressure changing portion 110 is configured to
differentiates the pressures of the operation fluids applied from
the travel operation device 47 to the hydraulic devices from each
other in a case where operation manners of the operation device
(the travel operation device) 47 is various.
[0226] For example, the pressure changing portion 110
differentiates a first pressure of the operation fluid from a
second pressure of the operation fluid. The first pressure is
applied from the operation valve 55 to the hydraulic devices such
as the travel pumps 53L and 53R in a case where the operation
member 54 is operated to one direction (for example, forward). The
second pressure is applied from the operation valve 55 to the
hydraulic devices such as the travel pumps 53L and 53R in a case
where the operation member 54 is operated to the other direction
(for example, backward).
[0227] For convenience of the explanation, the operation valve 55A
will be referred to as the first operation valve 55A, the operation
valve 55B will be referred to as the second operation valve 55B,
the operation valve 55C will be referred to as the third operation
valve 55C, and the operation valve 55D will be referred to as the
fourth operation valve 55D in the embodiment.
[0228] In particular, the pressure changing portion 110 includes a
first variable relief valve 121 and a second variable relief valve
122.
[0229] A port (an input port) of the first variable relief valve
121 is connected to the first operation valve 55A among the
operation valves 55 (the first operation valve 55A and the second
operation valve 55B) to be operated when the operation member 54 is
operated (moved) to a first direction.
[0230] A discharge fluid tube 111 is connected to a connection tube
(a connection path) 45d2 that is connected to an output port of the
first operation valve 55A. An input port of the first variable
relief valve 121 is connected to the discharge fluid tube 111.
[0231] The second variable relief valve 122 is connected to the
second operation valve 55B among the operation valves 55 (the first
operation valve 55A and the second operation valve 55B) to be
operated when the operation member 54 is operated (moved) to a
first direction.
[0232] A discharge fluid tube 112 is connected to the connection
tube (the connection path) 45d2 that is connected to an output port
of the second operation valve 55B. An input port of the second
variable relief valve 122 is connected to the discharge fluid tube
112.
[0233] The discharge fluid tube 111 and the discharge fluid tube
112 are confluent with each other on the downstream sides of the
first variable relief valve 121 and the second variable relief
valve 122. A relief valve 123 is disposed on a section being on a
downstream side of the confluence between the discharge fluid tube
111 and the discharge fluid tube 112. The discharge fluid tube 111
and the discharge fluid tube 112 are connected to the operation
fluid tank 22 and the like, the discharge fluid tube 111 and the
discharge fluid tube 112 being disposed on a downstream side of the
relief valve 123.
[0234] A pressure-receiving portion 121A of the first variable
relief valve 121 is connected to the third operation valve 55C and
the fourth operation valve 55D by a fluid tube (a fluid path) 113.
A pressure-receiving portion 122A of the second variable relief
valve 122 is connected to the third operation valve 55C and the
fourth operation valve 55D by the fluid tube (the fluid path)
113.
[0235] A check valve 114 is disposed on an intermediate portion of
the fluid tube 113. The check valve 114 includes a check valve 114a
and a check valve 114b. The check valve 114a is disposed on a fluid
tube (a fluid path) 113a connected to the operation valve 55D, the
fluid tube 113a being included in the fluid tube 113. The check
valve 114b is disposed on a fluid tube (a fluid path) 113b
connected to the operation valve 55D, the fluid tube 113b being
included in the fluid tube 113.
[0236] For example, in a case where the first operation valve 55A
being swingable is operated (moved) to the first direction (the
machine width direction), the third operation valve 55C and the
fourth operation valve 44D both being swingable may be operated
(moved) to a second direction (the forward direction and the
backward direction). In that case, the operations of the third
operation valve 55C and the fourth operation valve 55D change the
pressure of the operation fluids applied to the pressure-receiving
portions of the first variable relief valve 121 and the second
variable relief valve 122. In this manner, the set pressures of the
first variable relief valve 121 and the second variable relief
valve 122 can be reduced (lowered).
[0237] When the set pressures of the first variable relief valve
121 and the second variable relief valve 122 is equal to or more
than a predetermined pressure, the first variable relief valve 121
and the second variable relief valve 122 relief the operation
fluid, and thus the pressure applied to the second fluid tube 45
can be changed in the case where the first operation valve 55A is
operated.
[0238] That is, when the third operation valve 55C and the fourth
operation valve 55D are operated (moved) under the operation of the
first operation valve 55A, the pressures of the operation fluids
applied to the first travel fluid tube 45a and the third ravel
fluid tube 45c can be changed, and thus a turning speed of the work
machine 1 can be changed.
[0239] Additionally, in a case where the third operation valve 55C
and the fourth operation valve 55D are operated (moved) under the
operation of the second operation valve 55B to the other direction
(backward), the pressures of the operation fluids applied to the
second travel fluid tube 45b and the fourth ravel fluid tube 45d
can be changed, the pressures being generated when the second
operation valve 55B is operated by changing the set pressures of
the first variable relief valve 121 and the second variable relief
valve 122. That is, the turning speed of the work machine 1 can be
changed also in the case where the third operation valve 55C and
the fourth operation valve 55D are operated under the operation of
the second operation valve 55B.
[0240] As described above, the pressure changing portion 110
differentiates a third pressure of the operation fluid from a
fourth pressure of the operation fluid. The third pressure is
applied from the first operation valve 55A to the travel pumps 53L
and 53R in a case where the operation member 54 is operated to one
direction (for example, leftward). The fourth pressure is applied
from the second operation valve 55B to the travel pumps 53L and 53R
in a case where the operation member 54 is operated to the other
direction (for example, backward). In this manner, that
configuration improves a responsibility in starting the turn from
the straight traveling.
[0241] For convenience of the explanations, the operation valve 55A
is referred to as the first operation valve, the operation valve
55B is referred to as the second operation valve, the operation
valve 55C is referred to as the third operation valve, the
operation valve 55D is referred to as the fourth operation valve,
the valve connected to the input port of the first variable relief
valve 121 is referred to as the first operation valve, and the
valve connected to the input port of the second variable relief
valve 122 is referred to as the second operation valve in the
embodiment mentioned above. However, the first operation valve and
the second operation valve are not limited to the embodiment
described above. Each of the first operation valve and the second
operation valve may correspond to any one of the operation valve
55A, the operation valve 55B, the operation valve 55C, and the
operation valve 55D, and thus all of the combinations may be
employed.
[0242] In addition, the input port of the first variable relief
valve 121 may be connected to the third operation valve, and the
second variable relief valve 122 may be connected to the fourth
operation valve.
[0243] Moreover, the pressure changing portion 110 may
differentiate the pressure of the operation fluid applied from the
first operation valve or the second operation valve to the
hydraulic device from the pressure of the operation fluid applied
from the third operation valve or the fourth operation valve to the
hydraulic device.
[0244] The hydraulic system according to the embodiment easily
warms up the operation fluid in the fluid tube from the operation
valve for operating a hydraulic device to the hydraulic device. In
addition, the hydraulic system according to the embodiment improves
a responsibility of the anti-stall control, the anti-stall control
preventing the engine stall. Moreover, the hydraulic system
according to the embodiment improves the traveling performance of
the work machine. Furthermore, the hydraulic system according to
the embodiment easily brakes the work machine and releases the
braking.
Fourth Embodiment
[0245] FIG. 6 and FIG. 7 show a hydraulic system according to a
fourth embodiment of the present invention. The hydraulic system
according to the fourth embodiment can be applied to the hydraulic
systems according to the first embodiment to the third embodiment
described above. Thus, explanations of configurations similar to
the configurations of the first embodiment to the third embodiment
will be omitted.
[0246] In the embodiments described above, the traveling (the
forward traveling, the backward traveling, the leftward traveling,
and the rightward traveling) of the work machine 1 is controlled
singularly by the operation member 54. In the fourth embodiment,
the traveling of the work machine 1 is controlled by a plurality of
operation members. For example, the operation member (the operation
lever) 54 is arranged to the left of the operator seat 8, and the
operation member (the operation lever) 58 is arranged to the right
of the operator seat 8. Then, the operation valve 55 may be
operated by the two operation levers, the operation lever 54 and
the operation lever 58.
[0247] As shown in FIG. 6, the operation device 47 is arranged to
the left of the operator seat 8, and is capable of performing an
operation (a traveling operation) relating to the traveling of the
work machine 1 and an operation (a working operation) relating to
the working by the work machine 1.
[0248] As shown in FIG. 7, the operation device 48 is arranged to
the right of the operator seat 8, and is capable of performing the
operation (the traveling operation) relating to the traveling of
the work machine 1 and the operation (the working operation)
relating to the working by the work machine 1.
[0249] For convenience of the explanations, the operation device 47
will be referred to as a first operation device 47, and the
operation device 48 will be referred to as a second operation
device 48. In addition, the operation member 54 will be referred to
as a first operation member 54, and the operation member 58 will be
referred to as a second operation member 48.
[0250] The first operation member 54 is a lever configured to
perform a first operation to be moved in the forward direction and
the backward direction (in the first direction) and a second
operation to be moved in the machine width direction (in the second
direction). In the first operation member 54, the first operation
is allocated to the traveling operation, and the second operation
is allocated to the working operation.
[0251] That is, the first operation member 54 serves as both of an
operation member for traveling (a travel operation member) and an
operation member for working (a work operation member). Meanwhile,
the first operation member 54 is not limited to the lever, and may
be constituted of another member configured to at least perform the
first operation and the second operation independently.
[0252] The plurality of operation valves 55 are disposed on an
lower portion of the first operation member 54. The plurality of
operation valves 55 includes the operation valve 55A, the operation
valve 55B, the operation valve 55C, and the operation valve 55D.
The operation valve 55A, the operation valve 55B, the operation
valve 55C, and the operation valve 55D are connected to the
discharge fluid tube 40.
[0253] Each of the operation valve 55A and the operation valve 55B
is constituted of a valve that is configured to be operated in the
first operation, and provides the movements corresponding to the
traveling operation. Each of the operation valve 55C and the
operation valve 55D is constituted of a valve that is configured to
be operated in the second operation, and provides the movements
corresponding to the working operation.
[0254] The second operation member 58 is a lever configured to
perform a first operation to be moved in the forward direction and
the backward direction (in the first direction) and a second
operation to be moved in the machine width direction (in the second
direction). In the second operation member 54, the first operation
is allocated to the traveling operation, and the second operation
is allocated to the working operation.
[0255] That is, the second operation member 58 serves as both of an
operation member for traveling (a travel operation member) and an
operation member for working (a work operation member). Meanwhile,
the second operation member 58 is not limited to the lever, and may
be constituted of another member configured to at least perform the
first operation and the second operation independently.
[0256] The plurality of operation valves 59 are disposed on an
lower portion of the second operation member 58. The plurality of
operation valves 59 include the operation valve 59A, the operation
valve 59B, the operation valve 59C, and the operation valve 59D.
The operation valve 59A, the operation valve 59B, the operation
valve 59C, and the operation valve 59D are connected to the
discharge fluid tube 40.
[0257] Each of the operation valve 59A and the operation valve 59B
is constituted of a valve that is configured to be operated in the
first operation, and provides the movements corresponding to the
traveling operation. Each of the operation valve 59C and the
operation valve 59D is constituted of a valve that is configured to
be operated in the second operation, and provides the movements
corresponding to the working operation.
[0258] As described above, the operation valve 55A, the operation
valve 55B, the operation valve 59A, the operation device 59B of the
plurality of the operation valves is operated in accordance with
the traveling operation. The operation valve 55C, the operation
valve 55D, the operation valve 59C, the operation device 59D of the
plurality of the operation valves is operated in accordance with
the working operation.
[0259] For convenience of the explanation, each of the operation
valve 55A, the operation valve 55B, the operation valve 59A, the
operation device 59B may be referred to as a travel operation
valve. In addition, each of the operation valve 55C, the operation
valve 55D, the operation valve 59C, the operation device 59D may be
referred to as a work operation device.
[0260] Referring to FIG. 6 and FIG. 7, connections of the travel
operation valve and the work operation valve will be explained
next. Reference numerals (D1, D2, W1, and W2) shown in FIG. 6 and
FIG. 7 indicates the connection targets of the fluid tubes.
[0261] The travel operation valve is connected to the travel fluid
tube (the second fluid tube) 45. The travel fluid tube 45 includes
a first travel fluid tube 45a, a second travel fluid tube 45b, a
third travel fluid tube 45c, and a fourth travel fluid tube 45d. In
the embodiment, the first travel fluid tube 45a is constituted of a
fluid tube connected to the forward-movement pressure-receiving
portion 53a of the travel pump 53L and connected to the operation
valve 55A.
[0262] The second travel fluid tube 45b is constituted of a fluid
tube connected to the backward-movement pressure-receiving portion
53b of the travel pump 53L and connected to the operation valve
55B. The third travel fluid tube 45c is constituted of a fluid tube
connected to the forward-movement pressure-receiving portion 53a of
the travel pump 53R and connected to the operation valve 59A. The
fourth travel fluid tube 45d is constituted of a fluid tube
connected to the backward-movement pressure-receiving portion 53b
of the travel pump 53R and connected to the operation valve
59B.
[0263] When the first operation member 54 is tilted forward, a
pilot pressure is outputted from the operation valve 55A. The pilot
pressure is applied to the forward-movement pressure-receiving
portion 53a of the travel pump 53L. When the second operation
member 58 is tilted forward, a pilot pressure is outputted from the
operation valve 59A. The pilot pressure is applied to the
forward-movement pressure-receiving portion 53a of the travel pump
53R.
[0264] When the first operation member 54 is tilted backward, a
pilot pressure is outputted from the operation valve 55B. The pilot
pressure is applied to the backward-movement pressure-receiving
portion 53b of the travel pump 53L. When the second operation
member 58 is tilted backward, a pilot pressure is outputted from
the operation valve 59B. The pilot pressure is applied to the
backward-movement pressure-receiving portion 53b of the travel pump
53R.
[0265] Thus, when the first operation member 54 and the second
operation member 58 are tilted forward, the travel motor (the HST
motor) 36 turns forward at a speed proportional to the tilting
amounts (the swinging amounts) of the first operation member 54 and
the second operation member 58. As the result, the work machine 1
travels forward and straight.
[0266] When the first operation member 54 and the second operation
member 58 are tilted backward, the travel motor 36 turns backward
at a speed proportional to the tilting amounts (the tilting
extents) of the first operation member 54 and the second operation
member 58. As the result, the work machine 1 travels backward and
straight.
[0267] In addition, when one of the first operation member 54 and
the second operation member 58 is tilted forward and the other is
tilted backward, the travel motor 36 arranged to the left and the
travel motor 36 arranged to the right turn in different directions
from each other. As the result, the work machine 2 turns rightward
or leftward.
[0268] As described above, the forward and backward movements of
the first operation member 54 and the forward and backward
movements of the second operation member 58 provide the traveling
operations for making the work machine 1 travel forward, backward,
rightward, and leftward.
[0269] In addition, the work operation valve is connected to the
work fluid tube 43. The work fluid tube 43 includes a first work
fluid tube 43a, a second work fluid tube 43b, a third work fluid
tube 43c, and a fourth work fluid tube 43d.
[0270] The first work fluid tube 43a is constituted of a fluid tube
connected to the first control valve 56A and to the operation valve
55D. The second work fluid tube 43b is constituted of a fluid tube
connected to the first control valve 56A and to the operation valve
55C.
[0271] The third work fluid tube 43c is constituted of a fluid tube
connected to the second control valve 56B and to the operation
valve 59D. The fourth work fluid tube 43d is constituted of a fluid
tube connected to the second control valve 56B and to the operation
valve 59C.
[0272] When the first operation member 54 is tilted leftward, a
pilot pressure of the pilot fluid is set, the pilot fluid being to
be outputted from the operation valve 55D. The pilot pressure is
applied to the first control valve 56A, and thereby the boom
cylinder 14 is stretched to move the boom 10 upward.
[0273] When the first operation member 54 is tilted rightward, a
pilot pressure of the pilot fluid is set, the pilot fluid being to
be outputted from the operation valve 55C. The pilot pressure is
applied to the first control valve 56A, and thereby the boom
cylinder 14 is shortened to move the boom 10 downward.
[0274] When the second operation member 58 is tilted leftward, a
pilot pressure of the pilot fluid is set, the pilot fluid being to
be outputted from the operation valve 59D. The pilot pressure is
applied to the second control valve 56B, and thereby the bucket
cylinder 15 is shortened to make the bucket 11 perform the
shoveling movement.
[0275] When the second operation member 58 is tilted rightward, a
pilot pressure of the pilot fluid is set, the pilot fluid being to
be outputted from the operation valve 59C. The pilot pressure is
applied to the second control valve 56B, and thereby the bucket
cylinder 15 is stretched to make the bucket 11 perform the dumping
movement.
[0276] As described above, the rightward and leftward movements of
the first operation member 54 and the rightward and leftward
movements of the second operation member 58 provide the upward and
downward movements of the boom 10 and the working operations such
as the dumping movement and the shoveling movement of the
bucket.
[0277] The hydraulic system according to the fourth embodiment is
capable of releasing the braking state of the travel device 5 when
the travel operation valves (the operation valve 55A, the operation
valve 55B, the operation valve 59A, and the operation valve
59B).
[0278] For convenience of the explanations, the operation valve 55A
will be referred to as the first operation valve 55A, the operation
valve 55B will be referred to as the second operation valve 55B,
the operation valve 59A will be referred to as the third operation
valve 59A, and the operation valve 59B will be referred to as the
fourth operation valve 55C. The braking of the travel device 5 will
be explained below.
[0279] FIG. 8A and FIG. 8B are views illustrating the operation
device, the travel fluid tube, the braking device, and the
like.
[0280] As shown in FIG. 8A, a branched fluid tube 125 is connected
to the travel fluid tube (the second fluid tube) 45.
[0281] In particular, the branched fluid tube 125 includes a first
branched fluid tube 125a, a second branched fluid tube 125b, a
third branched fluid tube 125c, a fourth branched fluid tube 125d,
and a fifth branched fluid tube 125e.
[0282] The first branched fluid tube 125a is constituted of a fluid
tube branched from an intermediate portion of the first travel
fluid tube 45a. The second branched fluid tube 125b is constituted
of a fluid tube branched from an intermediate portion of the second
travel fluid tube 45b. The third branched fluid tube 125c is
constituted of a fluid tube branched from an intermediate portion
of the third travel fluid tube 45c. The fourth branched fluid tube
125d is constituted of a fluid tube branched from an intermediate
portion of the fourth travel fluid tube 45d.
[0283] The first branched fluid tube 125a and the third branched
fluid tube 125c are connected to a first select valve 131. The
second branched fluid tube 125b and the fourth branched fluid tube
125d are connected to a second select valve 132. The first select
valve 131 and the second select valve 132 are connected to the
fifth branched fluid tube 125e. The fifth branched fluid tube 125e
is provided with a third select valve 133.
[0284] The first select valve (shuttle valve) 131 includes an
output port 131a. The output port 131a is configured to output
higher one of a pressure of the operation fluid (the operation
fluid outputted from the first operation valve 55A) of the first
branched fluid tube 125a and a pressure of the operation fluid (the
operation fluid outputted from the third operation valve 59A) of
the third branched fluid tube 125c.
[0285] The second select valve (shuttle valve) 132 includes an
output port 132a. The output port 132a is configured to output
higher one of a pressure of the operation fluid (the operation
fluid outputted from the second operation valve 55B) of the second
branched fluid tube 125b and a pressure of the operation fluid (the
operation fluid outputted from the fourth operation valve 59B) of
the fourth branched fluid tube 125d.
[0286] The third select valve (shuttle valve) 133 includes an
output port 133a. The output port 133a is configured to output
higher one of a pressure of the operation fluid outputted from the
output port 131a of the first select valve 131 and a pressure of
the operation fluid outputted from the output port 132a of the
second select valve 132.
[0287] A fourth fluid tube 134 is connected to the output port 133a
of the third select valve (the shuttle valve) 133. The brake device
140 is connected to the fourth fluid tube 134. In addition, a fifth
fluid tube 135 is connected to an intermediate portion of the
fourth fluid tube 140. The fifth fluid tube 135 is constituted of a
discharge fluid tube configured to discharge (drain) the operation
fluid.
[0288] The brake device 140 is constituted of a device configured
to brake the travel device 5, a second disk, and releases the
braking. In particular, the brake device 140 includes a first disk
and a spring. The first disk is disposed on an output shaft of the
travel motor 36. The second disk is configured to be movable. The
spring pushed the second disk to the first disk such that the
second disk is contacted to the first disk.
[0289] In addition, the brake device 140 includes a housing portion
(a housing case) 140a. The housing portion 140a houses the first
disk, the second disk, and the spring. The fourth fluid tube 134 is
connected to a portion housing the second disk in the housing
portion 140a. In a storage portion of the housing portion 140a,
when the pilot fluid is supplied to satisfy a predetermined
pressure in the storage portion, the second disk is moved toward a
side opposite to a side of the braking, thereby releasing the
braking provided by the brake device 140.
[0290] On the other hand, when the pilot pressure is reduced to the
predetermined pressure or less in the storage portion of the
housing portion 140a, the second disk is moved toward a side where
the second disk is contacted to the first disk, thereby braking the
travel motor 36.
[0291] In this manner, when any one of the travel operation valves,
that is, the first operation valve 55A, the second operation valve
55B, the third operation valve 59, and the fourth operation valve
55C is operated, the pressure of the operation fluid outputted from
the operation valve having been operated is applied to the fourth
fluid tube 134 through the first select valve 131 and the second
select valve 132. Thus, the brake device 140 releases the braking
in the case where any one of the traveling operations (the forward
traveling, the backward traveling, and the turning) is performed,
that is, in the case where the first operation member 54 or the
second operation member 58 is operated.
[0292] Meanwhile, as shown in FIG. 8B, a check valve (a first check
valve) 141 may be disposed on the fourth fluid tube 134. The first
check valve 141 allows the operation fluid to flow from the third
select valve 133 to the brake device 140 and blocks the flowing of
the operation fluid flowing from the brake device 140 to the third
select valve 133.
[0293] In addition, a switch valve 137 may be disposed on the fifth
fluid tube 135. The switch valve 137 is constituted of a valve
configured to be switched to discharge (drain) the operation fluid
included in the fifth fluid tube 135, that is, a two-position
switch valve configured to be switched to a first position and to a
second position. The switch valve 137 is switched by a switch (a
parking switch) 145 connected to the control device 90 and the
like.
[0294] The parking switch 145 is a switch configured to be turned
on and tuned off. The control device 90 demagnetizes a solenoid of
the switch valve 137 to hold the switch valve 137 at the first
position in a case where the parking switch 145 is turned on. In
this manner, the operation fluid in the fifth fluid tube 135 is
discharged (drained) to the operation fluid tank 22 and the like
through the switch valve 137.
[0295] The control device 90 magnetizes the solenoid of the switch
valve 137 to hold the switch valve 137 at the second position in a
case where the parking switch 145 is turned off. In this manner,
the operation fluid in the fifth fluid tube 135 is not discharged
(drained) to the operation fluid tank 22 and the like.
[0296] That is, the operation fluids of the fifth fluid tube 135
and the fourth operation fluid 134 are discharged (drained) to the
operation fluid tank 22 and the like in the case where the switch
valve 137 is switched to the first position, and thus the brake
device 140 is set to be in the braking state.
[0297] On the other hand, the operation fluids of the fifth fluid
tube 135 and the fourth operation fluid 134 are not discharged
(drained) to the operation fluid tank 22 and the like in the case
where the switch valve 137 is switched to the second position, and
thus the brake device 140 is set to be in the released state.
[0298] A bypass fluid tube 144 may be disposed on each of the
fourth fluid tube 134 and the fifth fluid tube 135, the bypass
fluid tube 144 having a throttle portion 143 configured to reduce a
flow rate of the operation fluid.
[0299] Meanwhile, as shown in FIG. 8C, a pilot check valve 150 may
be disposed on the fourth fluid tube 134, and in this manner the
braking of the control device 140 can be released. In particular,
the discharge fluid tube 40 is provided with a branched fluid tube
151 branched from the discharge fluid tube 40. The brake device 140
is connected to the branched fluid tube 151.
[0300] A discharge fluid tube 152 is connected to an intermediate
portion of the branched fluid tube 151. A pilot check valve 10 is
disposed on the discharge fluid tube 152. The fourth fluid tube 134
is connected to a pressure-receiving portion 150a of the pilot
check valve 150.
[0301] In the hydraulic system shown in FIG. 8C, the pressure of
the operation fluid is increased in the fourth fluid tube 134 in
the case where any one of the traveling operations (the forward
traveling, the backward traveling, and the turning) is performed,
that is, in the case where the first operation member 54 or the
second operation member 58 is operated. The increased pressure of
the operation fluid is applied to the pressure-receiving portion
150a of the pilot check valve 150. When the pressure of the
operation fluid is applied to the pressure-receiving portion 150a
of the pilot check valve 150, the pilot check valve 150 is
closed.
[0302] In this manner, the pressure of the operation fluid of the
branched fluid tube 151 can be applied to the brake device 140, and
thereby the brake device 140 is set to be in the released
state.
[0303] Meanwhile, in a case where the traveling operation is not
performed, the pressure of the operation fluid of the fourth fluid
tube 134 is lowered (reduced), thereby the pilot check valve 150 is
opened. In this manner, the opening of the pilot check valve 150
reduces the pressure of the operation fluid in the branched fluid
tube 151, and thereby the brake device 140 is set to be in the
braking state.
[0304] The hydraulic system for the work machine mentioned above
includes the first select valve 131, the second select valve 132,
the third select valve 133, the fourth fluid tube 134, and the
brake device 140 connected to the fourth fluid tube 134. In this
manner, when the operation member 54 arranged to the left of the
operator seat 8 and the operation member 58 arranged to the right
of the operator seat 8 are operated, the control device 140 is
capable of releasing the braking of the travel device 5 only by
operating the operation members 54 and 58 in the work machine
configured to operate the travel device 5.
[0305] For example, when either one of the operation members 54 and
58 is operated, the pressure of the operation fluid can be applied
to the brake device 140, and thereby the braking is easily
released. In addition, when both of the operation members 54 and 58
are set to the neutral position, the brake device 140 easily brakes
the travel device 5.
[0306] In the embodiment mentioned above, the HST pump (the travel
pump) 66 and the travel motor 36 are controlled by the operation
fluid (the pilot fluid) under the HST control. However, the HST
pump (the travel pump) 66 and the travel motor 36 may be
electrically controlled.
[0307] That is, in the HST control, the swash plate of the travel
pump or the travel motor may be controlled by an electromagnetic
proportional valve and the like, and may be controlled by another
method.
[0308] In the embodiment mentioned above, the discharge fluid tube
configured to discharge (drain) the operation fluid is connected to
the operation fluid tank 22. However, the connection target of the
discharge fluid tube is not limited, and may be a suction portion
of the hydraulic pump and may be other portions.
[0309] In addition, each of the first hydraulic pump P1 and the
second hydraulic pump P2 may be constituted of a variable
displacement pump having a swash plate, and may be constituted of
another type of pump.
[0310] Each of the operation valves shown in FIG. 8 may be
constituted of a proportional valve having a potentiometer
configured to electrically detect the operation amounts (the
operation extents of the operation members 54 and 58.
[0311] In the embodiment mentioned above, the engine stall is
prevented by the first control device 90 controlling the aperture
of the operation valve (the proportional valve) 44. However,
instead of that configuration, the engine stall may be prevented by
the actuation valve of the variable relief valve 72 and the
like.
[0312] As shown in FIG. 9A, the engine stall may be prevented by
using the control lines L1 and L2 representing the relation between
the travel secondary pressure and the engine revolution speed. The
travel secondary pressure is a pressure of the operation fluid
flowing from the operation valves 55 (the operation valve 55A, the
operation valve 55B, the operation valve 55C, and the operation
valve 55D) to the travel pumps (the HST pumps) 53L and 53R in the
travel fluid tubes 45 (the first travel fluid tube 45a, the second
travel fluid tube 45b, the third travel fluid tube 45c, and the
fourth travel fluid tube 45d)
[0313] When the drop amount of the engine revolution speed is less
than a predetermined amount, the first control device 90 adjusts
the aperture of the actuation valve (the variable relief valve) 72
such that a relation between the travel secondary pressure and the
actual revolution speed of the engine corresponds to the control
line L1. In addition, when the drop amount of the engine revolution
speed is equal to or more than the predetermined amount, the first
control device 90 adjusts the aperture of the actuation valve (the
variable relief valve) 72 such that a relation between the travel
secondary pressure and the actual revolution speed of the engine
corresponds to the control line L2.
[0314] In a case where a fluid temperature of the operation fluid
measured by the measurement device 91 is high, the variable relief
valve 72 changes the aperture on the basis of the control lines L1
and L2 shown in FIG. 9A. Meanwhile, in a case where the fluid
temperature of the operation fluid measured by the measurement
device 91 is low, the set pressure of the variable relief valve 72
is changed by the first control device 90, and thereby the travel
secondary pressure can be adjusted so as not to be equal to or more
than the predetermined pressure as shown in the control lines L1
and L2 of FIG. 9B.
[0315] Meanwhile, values (upper limit vales of the travel secondary
pressure) of the control lines L1a, L1b, L2a, and L2b may be set on
the basis of the fluid temperature as shown in FIG. 9B. For
example, in a case where the fluid temperature is low, -15.degree.
C., the travel secondary pressure is set referring to the control
lines L1a and L2a. In addition, in a case where the fluid
temperature is low, -20.degree. C., the travel secondary pressure
is set referring to the control lines L1b and L2b. That is, the
lower the fluid temperature is, the more suppressed (the lower) the
travel secondary pressure is in the control lines L1 and L2.
[0316] The fluid temperatures at which the control lines L1a, L1b,
L2a, and L2b are set are not limited to the values described above.
In addition, the number of the control lines defining the travel
secondary pressure at the low temperature is not limited to the
number mentioned above. As described above, a plurality of control
lines defining the upper limitation of the travel secondary
pressure are prepared for each of predetermined low temperatures,
and thereby the work machine 1 is capable of warming up the
operation fluid even in traveling.
[0317] The hydraulic system according to the embodiment easily
warms up the operation fluid in the fluid tube from the operation
valve for operating a hydraulic device to the hydraulic device. In
addition, the hydraulic system according to the embodiment improves
a responsibility of the anti-stall control, the anti-stall control
preventing the engine stall. Moreover, the hydraulic system
according to the embodiment improves the traveling performance of
the work machine. Furthermore, the hydraulic system according to
the embodiment easily brakes the work machine and releases the
braking.
Fifth Embodiment
[0318] FIG. 10 shows a hydraulic system for travel employed as a
hydraulic system for a work machine according to a fifth embodiment
of the present invention. A whole configuration of the work machine
is similar to the configurations of the embodiments described
above. Thus, the explanations of the configurations will be
omitted.
[0319] As shown in FIG. 10, the hydraulic system includes a first
hydraulic pump P10, a left travel motor device (a first travel
motor device) 231L, a right travel motor (a second travel motor
device) 231R, a prime mover 32, and a travel drive device 234.
[0320] The first hydraulic pump P10 is configured to output the
operation fluid that is stored in the tank 22. The first hydraulic
pump P10 is a pump configured to be driven by a motive power of the
prime mover 32, and is constituted of a constant-displacement gear
pump. The first hydraulic pump P10 outputs the operation fluid
mainly used for the control.
[0321] For convenience of the explanation, the tank 22 for storing
the operation fluid is referred to as an operation fluid tank. In
addition, of the operation fluid outputted from the first hydraulic
pump P10, the operation fluid used for the control is referred to
as a pilot fluid, and a pressure of the pilot fluid is referred to
as a pilot pressure.
[0322] The output fluid tube (the output fluid path) 40 is disposed
on an output side of the first hydraulic pump P10, the output fluid
tube 40 being configured to supply the operation fluid (the pilot
fluid). The output fluid tube (a first fluid tube) 240 is provided
with the first travel motor device 231L and the second travel motor
device 231R.
[0323] The prime mover 32 is constituted of an electric motor, an
engine, or the like. In the embodiment, the prime mover 32 is the
engine. Meanwhile, the prime mover 32 may be a hybrid type having
the electric motor and the engine, and may be a type only having
the electric motor.
[0324] The travel drive device 234 is a device configured to drive
the first travel motor device 231L and the second travel motor
device 232R. The travel drive device 234 includes a drive circuit
(a left drive circuit) 234L and a drive circuit (a right drive
circuit) 234R, the drive circuit 234L being configured to drive the
first travel motor 231L, the drive circuit 234R being configured to
drive the second travel motor 231R.
[0325] Each of the left drive circuit 234L and the right drive
circuit 234R includes the travel pumps (travel hydraulic pumps)
253L and 253R, the speed-changing fluid tubes 257h and 257i, and a
second charge fluid tube 257j.
[0326] Each of the speed-changing fluid tubes 257h and 257i is a
fluid tube connecting the travel pumps 253L and 253R to the travel
motor 36. The second charge fluid tube 257j is a fluid tube
connected to the speed-changing fluid tubes 257h and 257i and
configured to charge the operation fluid from the first hydraulic
pump P10 to the speed-changing fluid tubes 257h and 257i.
[0327] Each of the travel pumps 253L and 253R is constituted of a
variable-displacement axial pump having a swash plate configured to
be driven by a motive power of the prime mover 32. Each of the
travel pumps 253L and 253R includes a forward-movement
pressure-receiving portion 253a and a backward-movement
pressure-receiving portion 253b. The pilot pressure is applied to
the forward-movement pressure-receiving portion 253a and to the
backward-movement pressure-receiving portion 253b. An angle of
swash plate is changed by the pilot pressure applied to the
forward-movement pressure-receiving portion 253a and to the
backward-movement pressure-receiving portion 253b.
[0328] The angle of the swash plate is changed, and thereby the
changing of the angle changes outputs of the travel pumps 253L and
253R (discharge amounts of the operation fluid) and an output
direction of the operation fluid.
[0329] The first travel motor device 231L is constituted of a motor
configured to supply a motive power to a drive shaft of the travel
device 5, the travel device 5 being disposed on the left side of
the machine body 2. The second travel motor device 231R is
constituted of a motor configured to supply a motive power to a
drive shaft of the travel device 5, the travel device 5 being
disposed on the right side of the machine body 2.
[0330] The first travel motor device 231L includes a travel motor
236, a forward-backward switch valve 235, and a travel control
valve (a hydraulic switch valve) 238. The operation fluid can be
supplied to the travel motor 236, to the forward-backward switch
valve 235, and to the travel control valve 238.
[0331] The travel motor 236 is constituted of a cam motor (a radial
piston motor). The travel motor 236 varies a displacement (a motor
displacement) in operating, and thereby changes revolutions and
torques of the output shaft.
[0332] In particular, the travel motor 236 includes a first motor
236A and a second motor 236B. When the first motor 236A and the
second motor 236B are driven, the motor displacement is increased,
and thereby the travel motor 236 is shifted to a first speed.
[0333] In addition, when either one of the first motor 236A and the
second motor 236B is driven, the motor displacement is decreased,
and thereby the travel motor 236 is shifted to a second speed.
[0334] The travel control valve 238 is constituted of a
two-position switch valve configured to be switched to a first
portion 238a and to a second position 238b. The travel control
valve 238 is switched by a switch 291 and the like.
[0335] In particular, the switch 291 is connected to the control
device 290. In a case where the travel control valve 238 is set to
the first speed by the switch 291, the control device 290 switches
a hydraulic switch valve connected to the pressure-receiving
portion of the travel control device 238 by a fluid tube, and
thereby switches the travel control valve 238 to the second
position 238b.
[0336] In a case where the travel control valve 238 is set to the
second speed by the switch 291, the control device 290 switches the
hydraulic switch valve, and thereby switches the travel control
valve 238 to the first position 238a. As described above, the
travel control valve 238 is switched, and thereby the speeds of the
travel motors 236 (the first motor 236A and the second motor 236B)
are changed.
[0337] A hydraulic system for work will be explained below.
[0338] As shown in FIG. 12, the hydraulic system includes a
plurality of control valves 56 and an operation hydraulic pump (a
second hydraulic pump) P20.
[0339] The second hydraulic pump P20 is constituted of a
constant-displacement gear pump that is a pump installed on a
position different from the position of the first hydraulic pump
P10. The second hydraulic pump P20 is configured to output the
operation fluid stored in the operation fluid tank 22. The second
hydraulic pup P20 outputs the operation fluid mainly used for
activating a hydraulic actuator.
[0340] A fluid tube (a main fluid path) 239 is disposed on an
output side of the second hydraulic pump P20. A plurality of
control valves 256 are connected to the main fluid tube 239. The
control valve 256 is constituted of a valve configured to switch a
flow direction of the operation fluid with use of the pilot
pressure of the pilot fluid.
[0341] In addition, the control valve 256 is a valve configured to
control (drive) the hydraulic actuators such as the boom, the
bucket, the hydraulic crusher, the hydraulic breaker, the angle
broom, the earth auger, the pallet fork, the sweeper, the mower,
the snow blower.
[0342] The plurality of control valves 256 include a first control
valve 256A, a second control valve 256B, and a third control valve
256C.
[0343] The first control valve 256A is a valve configured to
control the hydraulic cylinder (the boom cylinder) 14 for
controlling the boom. The second control valve 256B is a valve
configured to control the hydraulic cylinder (the bucket cylinder)
15 for controlling the bucket.
[0344] The third control valve 256C is a valve configured to
control the hydraulic actuators (the hydraulic cylinder, the
hydraulic motor) attached to an auxiliary attachment such as the
hydraulic crusher, the hydraulic breaker, the angle broom, the
earth auger, the pallet fork, the sweeper, the mower, the snow
blower.
[0345] Each of the first control valve 256A and the second control
valve 256B is constituted of three-position switch valve having a
direct-acting spool that is configured to be driven by the pilot
pressure. Each of the first control valve 256A and the second
control valve 256B is switched by the pilot pressure to a neutral
position, to a first position different from the neural position,
and to a second position different from the neutral position and
the first position.
[0346] The boom cylinder 14 is connected to the first control valve
256A by a fluid tube. The bucket cylinder 15 is connected to the
second control valve 256B by a fluid tube.
[0347] A supply-discharge fluid tube (a supply-discharge fluid
path) 283 is connected to the third control valve 256C.
[0348] One end of the supply-discharge fluid tube 283 is connected
to a supply-discharge port of the third control valve 256C. An
intermediate portion of the supply-discharge fluid tube 283 is
connected to the connection member 50. The other end of the
supply-discharge fluid tube 283 is connected to the auxiliary
hydraulic actuator.
[0349] In particular, the supply-discharge fluid tube 283 includes
a first supply-discharge fluid tube 283a. The first
supply-discharge fluid tube 283a connects a first supply-discharge
port of the third control valve 256C to a first port of the
connection member 50. In addition, the supply-discharge fluid tube
283 includes a second supply-discharge fluid tube 283b. The second
supply-discharge fluid tube 283b connects a second supply-discharge
port of the third control valve 256C to a second port of the
connection member 50.
[0350] That is, when the third control valve 256C is operated, the
operation fluid is supplied from the third control valve 256C
toward the first supply-discharge fluid tube 283a, and the
operation fluid is supplied from the third control valve 256C
toward the second supply-discharge fluid tube 283b.
[0351] As shown in FIG. 10, the first operation device 247 is
arranged to the left of the operator seat 8, and the second
operation device 248 is arranged to the right of the operator seat
8. the first operation device 247 and the second operation device
248 perform an operation (a traveling operation) relating to the
traveling of the work machine 1 and an operation (a working
operation) relating to the working by the work machine 1.
[0352] In other words, the first operation device 247 and the
second operation device 248 are operation devices configured to
operate the hydraulic devices for travel (the travel motor 236 and
the travel pumps 253L and 253R) and the hydraulic device for work
(the first control valve 256A, the second control valve 256B, the
third control valve 256C, the boom cylinder 14, the bucket cylinder
15, the hydraulic cylinder disposed on the auxiliary attachment,
and the hydraulic motor).
[0353] The first operation device 247 and the second operation
device 248 will be explained below in detail.
[0354] The first operation device 247 is constituted of a device
configured to perform both of the traveling operation and the
working operation, and includes a first operation member 254. The
first operation member 254 is a lever configured to perform a first
operation and a second operation, the first operation being moved
to the forward direction and to the backward direction, the second
operation being moved to the lateral direction (the machine width
direction) different from the forward direction and the backward
direction.
[0355] In other words, the second operation member 254 is
constituted of a lever configured to be moved in one direction (for
example, forward and leftward) and in the other direction (for
example, backward and rightward) different from the one
direction.
[0356] In the first operation member 254, the first operation is
allocated to the traveling operation, and the second operation is
allocated to the working operation. That is, the first operation
member 254 serves as both of an operation member for traveling (a
travel operation member) and an operation member for working (a
work operation member).
[0357] Meanwhile, the first operation member 254 is not limited to
the lever, and may be constituted of another member configured to
at least perform the first operation and the second operation
independently.
[0358] The plurality of operation valves 255 are disposed on an
lower portion of the first operation member 254. The plurality of
operation valves 255 includes the operation valve 255A, the
operation valve 255B, the operation valve 255C, and the operation
valve 255D. The operation valve 255A, the operation valve 255B, the
operation valve 255C, and the operation valve 255D are connected to
the discharge fluid tube 240.
[0359] The operation valve 255A is constituted of a valve activated
by the forward movement (the forward operation) of the first
operation (the forward movement and the backward movement). The
pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the forward
movement. The operation valve 255B is constituted of a valve
activated by the backward movement (the backward operation) of the
first operation (the forward movement and the backward movement).
The pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the backward
movement.
[0360] That is, each of the operation valve 255A and the operation
valve 255B is constituted of a valve that is configured to be
operated in the first operation, and provides the movements
corresponding to the traveling operation.
[0361] The operation valve 255C is constituted of a valve activated
by the leftward movement (the leftward operation) of the second
operation (the leftward movement and the rightward movement). The
pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the leftward
movement. The operation valve 255D is constituted of a valve
activated by the rightward movement (the rightward operation) of
the second operation (the leftward movement and the rightward
movement). The pressure of the operation fluid to be outputted is
changed in accordance with an operation amount (the operation) of
the rightward movement.
[0362] That is, each of the operation valve 255C and the operation
valve 255D is constituted of a valve that is configured to be
operated in the second operation, and provides the movements
corresponding to the working operation.
[0363] The second operation device 248 is constituted of a device
configured to perform both of the traveling operation and the
working operation, and includes a second operation member 258. The
second operation member 258 is a lever configured to perform a
first ration and a second operation, the first operation being
moved to the forward direction and to the backward direction, the
second operation being moved to the lateral direction (the machine
width direction) different from the forward direction and the
backward direction.
[0364] In other words, the second operation member 258 is
constituted of a lever configured to be moved in one direction (for
example, forward and leftward) and in the other direction (for
example, backward and rightward) different from the one
direction.
[0365] In the second operation member 258, the first operation is
allocated to the traveling operation, and the second operation is
allocated to the working operation. That is, the second operation
member 258 serves as both of an operation member for traveling (a
travel operation member) and an operation member for working (a
work operation member).
[0366] Meanwhile, the second operation member 258 is not limited to
the lever, and may be constituted of another member configured to
at least perform the first operation and the second operation
independently.
[0367] The plurality of operation valves 259 are disposed on an
lower portion of the second operation member 258. The plurality of
operation valves 259 include the operation valve 259A, the
operation valve 259B, the operation valve 259C, and the operation
valve 259D. The operation valve 259A, the operation valve 259B, the
operation valve 259C, and the operation valve 259D are connected to
the discharge fluid tube 240.
[0368] The operation valve 259A is constituted of a valve activated
by the forward movement (the forward operation) of the first
operation (the forward movement and the backward movement). The
pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the forward
movement. The operation valve 259B is constituted of a valve
activated by the backward movement (the backward operation) of the
first operation (the forward movement and the backward movement).
The pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the backward
movement.
[0369] That is, each of the operation valve 259A and the operation
valve 259B is constituted of a valve that is configured to be
operated in the first operation, and provides the movements
corresponding to the traveling operation.
[0370] The operation valve 259C is constituted of a valve activated
by the leftward movement (the leftward operation) of the second
operation (the leftward movement and the rightward movement). The
pressure of the operation fluid to be outputted is changed in
accordance with an operation amount (the operation) of the leftward
movement. The operation valve 259D is constituted of a valve
activated by the rightward movement (the rightward operation) of
the second operation (the leftward movement and the rightward
movement). The pressure of the operation fluid to be outputted is
changed in accordance with an operation amount (the operation) of
the rightward movement.
[0371] That is, each of the operation valve 259C and the operation
valve 259D is constituted of a valve that is configured to be
operated in the second operation, and provides the movements
corresponding to the working operation.
[0372] As described above, the operation valve 255A, the operation
valve 255B, the operation valve 259A, and the operation valve 259B
of the plurality of operations valves are operated corresponding to
the traveling operation. The operation valve 255C, the operation
valve 255D, the operation valve 259C, and the operation valve 259D
are operated corresponding to the working operation.
[0373] For convenience of the explanations, each of the operation
valve 255A, the operation valve 255B, the operation valve 259A, and
the operation valve 259B may be referred to as a travel operation
valve. Of the travel operation valves, the operation valve 255A is
referred to as "a first operation valve", the operation valve 255A
being configured to be activated by the movement to one direction
(for example, forward) of the first operation member 254. The
operation valve 255B is referred to as "a second operation valve",
the operation valve 255B being configured to be activated by the
movement to the other direction (for example, backward) of the
first operation member 254. The operation valve 259A is referred to
as "a third operation valve", the operation valve 259A being
configured to be activated by the movement to one direction (for
example, forward) of the second operation member 258. The operation
valve 259B is referred to as "a fourth operation valve", the
operation valve 259B being configured to be activated by the
movement to the other direction (for example, backward) of the
second operation member 258.
[0374] A relation between the travel operation valve, the work
operation valve, and the hydraulic device will be explained below.
Reference numerals "W10", "W20", "D10", and "D20" shown in FIG. 10
and FIG. 11 indicate connection targets of the fluid tubes.
[0375] The travel operation valve is connected to the travel pumps
253L and 253R by the travel fluid tube 245, the travel pumps 253L
and 253R being one of the hydraulic devices for travel (the travel
hydraulic devices). The travel fluid tube 245 includes a first
travel fluid tube 245a, a second travel fluid tube 245b, a third
travel fluid tube 245c, and a fourth travel fluid tube 245d.
[0376] The first travel fluid tube 245a is constituted of a fluid
tube connecting the first operation valve 255A to the
forward-movement pressure-receiving portion 253a of the travel pump
253L. The second travel fluid tube 245b is constituted of a fluid
tube connecting the second operation valve 255B to the
backward-movement pressure-receiving portion 253b of the travel
pump 253L.
[0377] The third travel fluid tube 245c is constituted of a fluid
tube connecting the third operation valve 259A to the
forward-movement pressure-receiving portion 253a of the travel pump
253R. The fourth travel fluid tube 245d is constituted of a fluid
tube connecting the fourth operation valve 259B to the
backward-movement pressure-receiving portion 253b of the travel
pump 253R.
[0378] When the second operation member 254 is titled forward, the
first operation valve 255A is operated to output the pilot pressure
from the first operation valve 255A. The pilot pressure is applied
to the forward-movement pressure-receiving portion 253a of the
travel pump 253L.
[0379] When the second operation member 258 is titled forward, the
third operation valve 259A is operated to output the pilot pressure
from the third operation valve 259A. The pilot pressure is applied
to the forward-movement pressure-receiving portion 253a of the
travel pump 253R.
[0380] When the first operation member 254 is titled backward, the
second operation valve 255B is operated to output the pilot
pressure from the second operation valve 255B. The pilot pressure
is applied to the backward-movement pressure-receiving portion 253b
of the travel pump 253L.
[0381] When the second operation member 258 is titled backward, the
fourth operation valve 259B is operated to output the pilot
pressure from the fourth operation valve 259B. The pilot pressure
is applied to the backward-movement pressure-receiving portion 253b
of the travel pump 253R.
[0382] In this manner, when the first operation member 254 and the
second operation member 258 are tilted forward, the travel motor
(the HST motor) 236 turns forward at a speed proportional to the
tilting amounts (the swinging amounts) of the first operation
member 254 and the second operation member 258. As the result, the
work machine 1 travels forward and straight.
[0383] When the first operation member 254 and the second operation
member 258 are tilted backward, the travel motor 236 turns backward
at a speed proportional to the tilting amounts (the tilting
extents) of the first operation member 254 and the second operation
member 258. As the result, the work machine 1 travels backward and
straight.
[0384] In addition, when one of the first operation member 254 and
the second operation member 258 is tilted forward and the other is
tilted backward, the travel motor 236 arranged to the left and the
travel motor 236 arranged to the right turn in different directions
from each other. As the result, the work machine 2 turns rightward
or leftward.
[0385] As described above, the forward and backward movements of
the first operation member 254 and the forward and backward
movements of the second operation member 258 provide the traveling
operations for making the work machine 1 travel forward, backward,
rightward, and leftward.
[0386] In addition, the work operation valve is connected to the
control valve 256 by the work fluid tube 246, the control valve 256
being one of the hydraulic devices for work (the operation
hydraulic devices). The work fluid tube 246 includes a first work
fluid tube 246a, a second work fluid tube 246b, a third work fluid
tube 246c, and a fourth work fluid tube 246d.
[0387] The first work fluid tube 246a is constituted of a fluid
tube connecting the operation valve 255C to a pressure-receiving
portion of the first control valve 256A. The second work fluid tube
246b is constituted of a fluid tube connecting the operation valve
255D to the pressure-receiving portion of the first control valve
256A.
[0388] The third work fluid tube 246c is constituted of a fluid
tube connecting the operation valve 259C to a pressure-receiving
portion of the second control valve 256B. The fourth work fluid
tube 246d is constituted of a fluid tube connecting the operation
valve 259D to the pressure-receiving portion of the second control
valve 256B.
[0389] When the first operation member 254 is tilted leftward, the
operation valve 255C is operated to set the pilot pressure of the
pilot fluid, the pilot fluid being outputted from the operation
valve 255C. The pilot pressure is applied to the pressure-receiving
portion of the first control valve 256A, and thereby the boom
cylinder 14 is stretched to move the boom 10 upward.
[0390] When the first operation member 254 is tilted rightward, the
operation valve 255D is operated to set the pilot pressure of the
pilot fluid, the pilot fluid being outputted from the operation
valve 255D. The pilot pressure is applied to the pressure-receiving
portion of the first control valve 256A, and thereby the boom
cylinder 14 is shortened to move the boom 10 downward.
[0391] When the second operation member 258 is tilted leftward, the
operation valve 259C is operated to set the pilot pressure of the
pilot fluid, the pilot fluid being outputted from the operation
valve 259C. The pilot pressure is applied to the pressure-receiving
portion of the second control valve 256B, and thereby the bucket
cylinder 15 is shortened to make the bucket 11 perform the
shoveling movement.
[0392] When the second operation member 258 is tilted rightward,
the operation valve 259D is operated to set the pilot pressure of
the pilot fluid, the pilot fluid being outputted from the operation
valve 259D. The pilot pressure is applied to the pressure-receiving
portion of the second control valve 256B, and thereby the bucket
cylinder 15 is stretched to make the bucket 11 perform the dumping
movement.
[0393] As described above, the rightward and leftward movements of
the first operation member 254 and the rightward and leftward
movements of the second operation member 258 provide the upward and
downward movements of the boom 10 and the working operations such
as the dumping movement and the shoveling movement of the
bucket.
[0394] Meanwhile, the hydraulic system is provided with a circuit
capable of reducing a pressure (depressurizing) the operation fluid
of the travel fluid tube 245.
[0395] As shown in FIG. 11, a discharge fluid tube 251 for
discharging the operation fluid is connected to a travel fluid tube
(a travel fluid path) 245 that connects the travel operation valve
to the travel pumps 253L and 253R, one of the hydraulic
devices.
[0396] An actuation valve 270A is disposed on the discharge fluid
tube 251. The actuation valve 270 is constituted of a valve
configured to reduce a pressure of the operation fluid in the
discharge fluid tube 251, that is, a valve configured to reduce a
pressure of the operation fluid in the travel fluid tube 245 that
is connected to the discharge fluid tube 251.
[0397] In other words, the actuation valve 270A is constituted of a
valve configured to reduce a pressure (a secondary pressure) of the
operation fluid set by at least one of the plurality of operation
valves 255.
[0398] The discharge fluid tube 251 and the actuation valve 270A
will be explained below in detail.
[0399] The discharge fluid tube 251 is a fluid tube connected to
the travel operation valve, that is, at least one of the first
operation valve 255A, the second operation valve 255B, the third
operation valve 259A, and the fourth operation valve 259B.
[0400] In particular, the discharge fluid tube 251 includes a first
discharge fluid tube 251a, a second discharge fluid tube 251b, a
third discharge fluid tube 251c, a fourth discharge fluid tube
251d, and a fifth discharge fluid tube 251e.
[0401] The first discharge fluid tube 251a is a fluid tube
branching from an intermediate portion of the first travel fluid
tube 245a. The second discharge fluid tube 251b is a fluid tube
branching from an intermediate portion of the second travel fluid
tube 245b.
[0402] The third discharge fluid tube 251c is a fluid tube
branching from an intermediate portion of the third travel fluid
tube 245c. The fourth discharge fluid tube 251d is a fluid tube
branching from an intermediate portion of the fourth travel fluid
tube 245d.
[0403] The fifth discharge fluid tube 251e is a fluid tube
connecting the first discharge fluid tube 251a, the second
discharge fluid tube 251b, the third discharge fluid tube 251c, and
the fourth discharge fluid tube 251d. An actuation valve 270A is
disposed on an intermediate portion of the fifth discharge fluid
tube 251c.
[0404] A check valve 271 is disposed on each of the first discharge
fluid tube 251a, the second discharge fluid tube 251b, the third
discharge fluid tube 251c, and the fourth discharge fluid tube
251d. The check valve 271 is configured to allow the operation
fluid to flow from the travel fluid tube 245 toward the fifth
discharge fluid tube 251e (the actuation valve 270A) and blocks the
flowing of the operation fluid flowing from the discharge side
toward the fifth discharge fluid tube 251e (the actuation valve
270A).
[0405] The actuation valve 270A includes a relief valve 278
configured to change the set pressure of the actuation valve 270A.
For example, the relief valve 278 is constituted of a balanced
relief valve configured to vary the set pressure on the basis of a
pressure of the operation fluid, and includes a pressure-receiving
portion 78a configured to receive a pressure of the operation
fluid. In addition, the relief valve 278 may be constituted of a
variable relief valve.
[0406] When a pressure of the operation fluid is applied to the
pressure-receiving portion 78a, the set pressure is varied in
accordance with a pressure of the operation fluid applied to the
pressure-receiving portion 78a. For example, the set pressure is
increased in accordance with increment of the pressure of the
operation fluid applied to the pressure-receiving portion 78a, and
the set pressure is decreased in accordance with decrement of the
pressure of the operation fluid applied to the pressure-receiving
portion 78a.
[0407] In addition, the actuation valve 270A includes a
proportional valve 273. The proportional valve 273 is connected to
the pressure-receiving portion 78a of the relief valve 278 by the
fluid tube 72. The output fluid tube 240 is connected to the
proportional valve 273, and the operation fluid can be supplied
from the first hydraulic pump P10 to the proportional valve 273.
The proportional valve 273 is constituted of an electromagnetic
proportional valve configured to magnetize the solenoid of the
proportional valve 273 to change the aperture of the proportional
valve 273. The proportional valve 273 is controlled by the control
device 290.
[0408] For example, the control device 290 outputs a control signal
to magnetize the solenoid of the proportional valve 273 in
accordance with a degree of the suppression in a case of
suppressing a traveling speed of the work machine even when the
traveling operation is performed. In this manner, the aperture of
the proportional valve 273 is increased and decreased on the basis
of the control signal from the control device 290.
[0409] When the pressure of the operation fluid applied to the
pressure-receiving portion 78a of the relief valve 278, the set
pressure of the relief valve 278 is reduced, and the operation
fluid in the travel fluid tube 245 is discharged (drained) to the
operation fluid tank and the like through the discharge fluid tube
251. In this manner, a revolution speed of the travel motor 236 is
reduced, and thereby a traveling speed of the work machine is
suppressed.
[0410] For example, in a case of forbidding the traveling of the
work machine, the control device 290 outputs a control signal to
minimize the aperture of the proportional valve 273. In this
manner, the aperture of the proportional valve 273 is minimized,
the pressure of the operation fluid applied to the
pressure-receiving portion 278a of the relief valve 278 is
minimized, and thereby the set pressure of the relief valve 278 is
minimized.
[0411] When the set pressure of the relief valve 278 is minimized,
almost of all the operation fluid in the travel fluid tube 245 is
discharged (drained) to the operation fluid tank and the like
through the discharge fluid tube 251, and thereby the revolution
speed of the travel motor 236 falls to zero. In this manner, the
traveling of the work machine can be forbidden, that is, the
traveling can be stopped.
[0412] Thus, when the pressure on the secondary side of the travel
operation valve is fallen to zero by the proportional valve 273,
the work device 4 can be operated with the work machine 1
stopped.
[0413] In the embodiment described above, the relief valve 278 is
constituted of a valve that has the pressure-receiving portion 278a
configured to receive a pressure of the operation fluid and is
configured to reduce the set pressure with use of the pressure of
the operation fluid applied to the pressure-receiving portion 278a.
However, the relief valve 278 may be constituted of an
electromagnetic proportional relief valve instead of that
valve.
[0414] In that case, the control device 290 directly changes the
set pressure of the relief valve 278 without the proportional valve
273 mentioned above by outputting a control signal to the relief
valve 278.
[0415] Meanwhile, the travel fluid tube (fluid path) 245 may be
provided with a check valve and a throttle portion. In particular,
a check valve 274 is disposed on each of the first travel fluid
tube 245a, the second travel fluid tube 245b, the third travel
fluid tube 245d, and the fourth travel fluid tube 245e.
[0416] The check valve 274 allows the operation fluid to flow from
the operation valve side (for example, the first operation valve
255A) to the side of the relief valve 278 and blocks the flowing of
the operation fluid flowing from the side of the relief valve 278
to the operation valve side.
[0417] A bypass fluid tube (a bypass fluid path) 275 is disposed on
an inlet side and an outlet side of the check valve 274, and a
throttle portion 276 is disposed on the bypass fluid tube 275. In
addition, a throttle portion 277 is disposed on a section of the
travel fluid tube 245 between the check valve 274 and a connecting
portion connected to the discharge fluid tube 251.
[0418] FIG. 12A is a view illustrating a first modified example of
the hydraulic system. FIG. 12B is a view illustrating a second
modified example of the hydraulic system. The modified examples
will be explained below.
[0419] As shown in FIG. 12A, an actuation valve 270B includes a
pilot check valve 181 and a switch valve 282. The pilot check valve
181 is configured to block the discharging of the operation fluid
in the discharge fluid tube 251 on the basis of the pressure of the
operation fluid applied to the pressure-receiving portion 281a. The
switch valve 282 is connected to the pilot check valve 181 by the
fluid tube 272.
[0420] The switch valve 282 is a switch valve configured to be
switched to a first position 282A and to a second position 282B,
and is constituted of a two-position switch valve configured to
magnetize the solenoid to be switched to the positions, for
example. The switch valve 282 is switched to the first position
282A or to the second position 282B in accordance with the control
signal of the control device 290.
[0421] When the pressure of the operation fluid applied to the
pressure-receiving portion 281a of the pilot check valve 181 is
equal to or more than a predetermined value after the switch valve
282 is switched to the first position 282A, the pilot check valve
181 is closed to block the discharging of the operation fluid in
the discharge fluid tube 251.
[0422] Thus, when the pilot check valve 181 blocks the discharging
of the operation fluid of the discharge fluid tube 251, the
pressure of the operation fluid in the travel fluid tube 245 is
increased and decreased in accordance with the traveling operation.
In this manner, the first operation device 247 and the second
operation device 248 are capable of changing the revolution speed
of the travel motor 236.
[0423] On the other hand, when the pressure of the operation fluid
applied to the pressure-receiving portion 281a of the pilot check
valve 181 is equal to or more than a predetermined value after the
switch valve 282 is switched to the second position 282B in
accordance with the control signal of the control device 290, the
pilot check valve 181 is opened to allows the operation fluid in
the discharge fluid tube 251 to be discharged (drained).
[0424] Thus, when the pilot check valve 181 allows the operation
fluid in the discharge fluid tube 251 to be discharged (drained),
the operation fluid in the travel fluid tube 245 is discharged
(drained) from the discharge fluid tube 251 to the operation fluid
tank 22 and the like.
[0425] As the result, both of the first operation device 247 and
the second operation device 248 are capable of reducing the
revolution speed of the travel motor 236, thereby suppressing the
traveling speed of the work machine and forbidding the traveling of
the wok machine.
[0426] Meanwhile, the pilot check valve 181 is closed when the
pressure of the operation fluid applied to the pressure-receiving
portion 281a is equal to or more than a predetermined value and is
opened when the pressure of the fluid tube is less than the
predetermined value. However, instead of that configurations, the
pilot check valve may be opened when the pressure of the operation
fluid applied to the pressure-receiving portion 281a is equal to or
more than a predetermined value and is closed when the pressure of
the fluid tube is less than the predetermined value.
[0427] In that case, the switch valve 282 is switched to the first
position 282A in the case of suppressing the traveling speed of the
work machine or forbidding the traveling of the work machine.
[0428] As shown in FIG. 12B, the actuation valve 270C is
constituted of a switch valve configured to be switched to a first
position 270C1 and to a second position 270C2, the first position
270C1 being provided for allowing the operation fluid in the
discharge fluid tube 251 to be discharged (drained), the second
position 270C2 being provided for blocking the discharging of the
operation fluid in the discharge fluid tube 251. For example, the
actuation valve 270C is constituted of a two-position switch valve
configured to magnetize the solenoid to be switched.
[0429] The switch valve 270C is connected to the control device
290, and is switched to the first position 270C1 or the second
position 270C2 in accordance with the control signal. In the case
of suppressing the traveling speed of the work machine or
forbidding the traveling of the work machine, the control device
290 switches the switch valve 270C to the first position 270C1. In
the case of allowing the traveling of the work machine in
accordance with the traveling operation, the control device 290
switches the switch valve 270C to the second position 270C2.
[0430] In the embodiment mentioned above, all of the first travel
fluid tube 245a, the second travel fluid tube 245b, the third
travel fluid tube 245c, and the fourth travel fluid tube 245d are
connected to the discharge fluid tube 251. However, the discharge
fluid tube 251 may be disposed on any one of the first travel fluid
tube 245a, the second travel fluid tube 245b, the third travel
fluid tube 245c, and the fourth travel fluid tube 245d, and any one
of the actuation valve 270A, the actuation valve 70B, and the
actuation valve 70C.
[0431] In other words, any one of the actuation valve 270A, the
actuation valve 70B, and the actuation valve 70C may be disposed on
the discharge fluid tube 251 connected to at least one of the first
operation valve 255A, the second operation valve 255B, the third
operation valve 259A, and the fourth operation valve 259B.
[0432] In this manner, the movements of the hydraulic devices for
travel can be suppressed or forbidden under the various conditions.
For example, the traveling of the work machine such as the forward
traveling, the backward traveling, the rightward turning, and the
leftward turning can be suppressed (restricted).
[0433] In addition, the discharge fluid tube 251 may be disposed on
the work fluid tube 246, and any one of the actuation valves 270A,
270B, and 270C may be disposed on the discharge fluid tube 251.
[0434] In other words, the operation valve 255C serves as the first
operation valve, the operation valve 255D serves as the second
operation valve, the operation valve 259C serves as the third
operation valve, the operation valve 259D serves as the fourth
operation valve. And furthermore, any one of the actuation valves
270A, 270B, and 270C may be disposed on the discharge fluid tube
251 connected to at least one of the first operation valve 255C,
the second operation valve 255D, the third operation valve 259C,
and the fourth operation valve 259D.
[0435] In this manner, the movements of the hydraulic devices for
work can be suppressed or forbidden under the various
conditions.
[0436] The discharge fluid tube 251 may be disposed on both of the
travel fluid tube 245 and the work fluid tube 246, and further any
one of the actuation valves 270A, 270B, and 270C may be disposed on
the discharge fluid tube 251.
[0437] The check valve 274, the bypass fluid tune 275, the throttle
portions 276 and 277 may be employed in the case where the
discharge fluid tube 251 is disposed on the fluid tubes (the travel
fluid tube 245 and the work fluid tube 246).
[0438] In addition, the actuation valve is constituted of a valve
configured to perform the control relating to the discharging of
the operation fluid in the discharge fluid tube 251, and is not
limited to the actuation valves 270A, 270B, and 270C mentioned
above.
[0439] The check valve for setting the differential pressure may be
disposed on the fluid tube on the downstream side connected to the
discharge fluid tube 251 or to the pressure-receiving portion
70a.
[0440] Rates of springs of the check valves 71 may be different in
each of the first discharge fluid tube 251a, the second discharge
fluid tube 251b, the third discharge fluid tube 251c, the fourth
discharge fluid tube 251d, and the fifth discharge fluid tube
251e.
[0441] A hydraulic system for a work machine includes a hydraulic
pump configured to output an operation fluid, a hydraulic device
configured to be operated by the operation fluid, an operation
member configured to operate the hydraulic device, a plurality of
operation valves configured to change a pressure of the operation
fluid in accordance with the operation of the operation member, a
discharge fluid tube connected to at least one of the plurality of
operation valves, the discharge fluid tube being configured to
discharge (drain) the operation fluid, and an operation valve
disposed on the discharge fluid tube, the operation valve being
configured to reduce the pressure of the operation fluid in the
discharge fluid tube.
[0442] A hydraulic system for a work machine includes a hydraulic
pump configured to output an operation fluid, a hydraulic device
configured to be operated by the operation fluid, a first operation
device configured to operate the hydraulic device, including a
first operation member configured to be operated (moved) to one
direction and to the other direction, a first operation valve
configured to change a pressure of the operation fluid in
accordance with the movement of the first operation member to the
one direction, and a second operation valve configured to change
the pressure of the operation fluid in accordance with the movement
of the first operation member to the other direction, a second
operation device configured to operate the hydraulic device,
including a second operation member configured to be operated
(moved) to one direction and to the other direction, a third
operation valve configured to change a pressure of the operation
fluid in accordance with the movement of the second operation
member to the one direction, and a fourth operation valve
configured to change the pressure of the operation fluid in
accordance with the movement of the second operation member to the
other direction, a discharge fluid tube connected to at least one
of the first operation valve, the second operation valve, the third
operation valve, and the fourth operation valve, the discharge
fluid tube being configured to discharge (drain) the operation
fluid, and an operation valve disposed on the discharge fluid tube,
the operation valve being configured to reduce the pressure of the
operation fluid in the discharge fluid tube.
[0443] The operation valve includes a relief valve configured to
change the set pressure.
[0444] The operation valve includes a proportional valve connected
to a pressure-receiving portion of the relief valve, the
proportional valve being configured to change a pressure of the
operation fluid applied to the pressure-receiving portion.
[0445] The hydraulic system mentioned above includes a fluid tube
connecting the plurality of operation valves to the hydraulic
device and being connected to the discharge fluid tube, and a check
valve disposed on the discharge fluid tube, the check valve being
configured to allow the operation fluid to flow from the fluid tube
toward the operation valve and blocks the flowing of the operation
fluid from a discharge side toward the fluid tube.
[0446] The hydraulic system mentioned above includes a fluid tube
connecting the hydraulic device to the first operation valve, to
the second operation valve, to the third operation valve, and to
the fourth operation valve and being connected to the discharge
fluid tube, and a check valve disposed on the discharge fluid tube,
the check valve being configured to allow the operation fluid to
flow from the fluid tube toward the operation valve and blocks the
flowing of the operation fluid from a discharge side toward the
fluid tube.
[0447] The operation valve includes a pilot check valve configured
to block the discharging of the operation fluid in the discharge
fluid tube on the basis of the pressure of the operation fluid
applied to the pressure-receiving portion.
[0448] The operation valve includes a switch valve configured to be
switched between a first position and a second position, the first
position being to allow the discharging of the operation fluid in
the discharge fluid tube, the second position being to block the
discharging of the operation fluid in the discharge fluid tube.
[0449] The hydraulic device is a travel pump configured to change
an output on the basis of the pressure of the operation fluid.
[0450] The hydraulic system according to the embodiment is capable
of easily reducing (lowering) the pressure in the fluid tube
connected to the hydraulic system and the like.
Sixth Embodiment
[0451] FIG. 13 illustrates a hydraulic system for travel serving as
a hydraulic system for the work machine according to a sixth
embodiment of the present invention. The work machine according to
the present embodiment has the configurations similar to the
configurations of the work machine described in the above-mentioned
embodiments. Thus, the explanation of the configurations of the
work machine will be omitted. A hydraulic system for travel
illustrated in FIG. 13 is similar to the hydraulic system for
travel according to the fifth embodiment. Thus, the explanation of
the same configurations will be omitted.
[0452] Each of a travel pump 253L and a travel pump 253R is
constituted of a variable displacement axial pumps having a swash
plate (a variable displacement pump) that is configured to be
driven by a motive power of the prime mover 32. For convenience of
the explanation, the travel pump 253L may be referred to as a first
variable displacement pump, and the travel pump 253R may be
referred to as a second variable displacement pump.
[0453] Each of the travel pump (the first variable displacement
pump) 253L and the travel pump (the second variable displacement
pump) 253R includes the forward-movement pressure-receiving portion
53a and the backward-movement pressure-receiving portion 53b. The
pilot pressure is applied to a forward-movement pressure-receiving
portion 253a and a backward-movement pressure-receiving portion
253b.
[0454] An angle of the swash plate is changed by the pilot pressure
applied to a forward-movement pressure-receiving portion 253a and
the backward-movement pressure-receiving portion 253b. When the
angle of the swash plate is changed, the changing changes the
outputs (output amounts of the operation fluid, that is, a
displacement) of the travel pump (the first variable displacement
pump) 253L and the travel pump (the second variable displacement
pump) 253R and changes the directions of the outputs of the
operation fluid.
[0455] Thus, the first operation device 247 and the second
operation device 248 are operation devices configured to change at
least the displacement of the travel pump (the first variable
displacement pump) 253L and the displacement of the travel pump
(the second variable displacement pump) 253R.
[0456] An operation valve 370 includes a relief valve 378 and a
proportional valve 373. The relief valve 378 is configured to
change a set pressure of the relief valve 378. The proportional
valve 373 is connected to the relief valve 378 by a fluid tube (a
fluid path) 272. For example, the relief valve 378 is a balanced
relief valve configured to vary a set pressure of the relief valve
378 on the basis of the pressure of the operation fluid. The relief
valve 378 has a pressure-receiving portion 378a configured to
receiving the pressure of the operation fluid.
[0457] The fluid tube 272 is connected to the pressure-receiving
portion 378a of the relief valve 378. The proportional valve 373 is
connected to the fluid tube 272. An output fluid tube (an output
fluid path) 40 is connected to the proportional valve 373, and thus
the operation fluid from a first hydraulic pump P100 can be
supplied to the proportional valve 373.
[0458] The proportional valve 373 is an electromagnetic
proportional valve configured to magnetize a solenoid to change an
aperture of the electromagnetic proportional valve, and is
controlled by the control device (the controller) 390. For example,
the control device 390 outputs a control signal to the proportional
valve 373, and thereby increases and decreases the aperture of the
proportional valve 373.
[0459] When the aperture of the proportional valve 373 is increased
and decreased, the pressure of the operation fluid also changes in
accordance with the increasing and decreasing of the aperture, the
pressure being applied to the pressure-receiving portion 378a of
the relief valve 378. In this manner, the set pressure of the
relief valve 378 is changed.
[0460] For example, when the set pressure of the relief valve 378
is low, the operation fluid of the travel fluid tube 245 is
discharged (drained) through the discharge fluid tube 251. In this
manner, the pressure of the operation fluid applied to the travel
fluid tube 245 is reduced.
[0461] As described above, the pressure of the operation fluid is
reduced in the travel fluid tube 245, and thereby the pressures of
the operation fluid applied to the forward-movement
pressure-receiving portion 253a and to the backward-movement
pressure-receiving portion 253b are reduced in the travel pump 253L
and the travel pump 253R.
[0462] That is, the control device 390 and the operation valves 370
(the relief valve 378 and the proportional valve 373) are capable
of changing the displacements of the travel pump 253L and the
travel pump 253R independently from the operations of the operation
devices (the first operation device 247 and the second operation
device 248).
[0463] A control to the operation valves 370 performed by the
control device 390 will be explained below.
[0464] A revolution speed detection device (a detection device) 301
and a temperature detection device (a detection device) 302 are
connected to the control device 390. The revolution speed detection
device 301 is a device configured to detect a revolution speed of
the prime mover. The revolution speed detection device 301 detects
an engine revolution speed in a case where the prime mover is an
engine, and detects a motor revolution speed in a case where the
prime mover is an electric motor. The temperature detection device
302 measures a temperature of the operation fluid (referred to as a
fluid temperature).
[0465] The control device 390 controls a revolution speed of the
prime mover, and controls a set value of the relief valve 378, that
is, the pressure in the travel fluid tube 245 in accordance with
the fluid temperature detected by the temperature detection device
302. The revolution speed of the prime mover is detected by the
revolution speed detection device 301.
[0466] For convenience of the explanation, the revolution speed of
the prime mover is the engine revolution speed. In addition, the
pressure in the travel fluid tube 245 is referred to as "a
temperature-restricting pressure", the pressure being controlled on
the basis of the engine revolution speed and the fluid
temperature.
[0467] The control device 390 includes a first pressure-setting
circuit (a first pressure-setting portion) 390A. The first
pressure-setting circuit 390A is configured to set the
temperature-restricting pressure. The first pressure-setting
circuit 390A is constituted of a computer program stored in the
control device 390, an electric circuit, an electronic circuit, or
the like.
[0468] The first pressure-setting circuit 390A sets the set
pressure (the temperature-restricting pressure) of the relief valve
378 on the basis of the engine revolution speed and the fluid
temperature. In the embodiment, the first pressure-setting circuit
390A sets the set pressure (the temperature-restricting pressure)
of the relief valve 378 on the basis of a plurality of threshold
values related to the operation fluid (a plurality of threshold
values related to the fluid temperature) and the engine revolution
speed set in accordance with the plurality of threshold values.
[0469] The first pressure-setting circuit 390A may set the
temperature-restricting pressure of the relief valve 378 on the
basis of the engine revolution speed and one of the fluid
temperatures.
[0470] FIG. 15 is a view illustrating a relation between the engine
revolution speed, the fluid temperature, and the set pressure of
the relief valve 378 (the temperature-restricting pressure).
[0471] The control device 390 stores a first control information (a
first control map) showing a relation between the engine revolution
speed and the temperature-restricting pressure for each of the
plurality of the fluid temperatures, for example.
[0472] For example, the control device 390 stores a first control
line L1, a second control line L2, a third control line L3, and a
fourth control line IA. The first control line L1 shows a relation
between the engine revolution speed and the temperature-restricting
pressure under a condition where the fluid temperature is
-30.degree. C. (degrees) or less. The second control line L2 shows
a relation between the engine revolution speed and the
temperature-restricting pressure under a condition where the fluid
temperature is -20.degree. C. (degrees). The third control line L3
shows a relation between the engine revolution speed and the
temperature-restricting pressure under a condition where the fluid
temperature is -10.degree. C. (degrees). The fourth control line L4
shows a relation between the engine revolution speed and the
temperature-restricting pressure under a condition where the fluid
temperature is 0.degree. C. (degrees) or more.
[0473] In other words, the control device 390 has a plurality of
control lines (the first control line L10, the second control line
L20, the third control line L30, and the fourth control line L40)
representing a plurality of threshold values of the fluid
temperature (-30.degree. C., -20.degree. C., -10.degree. C., and
0.degree. C.).
[0474] Meanwhile, the control device 390 may store a function (a
control function) serving as the first control information, the
function being used for calculating the plurality of control lines
(the first control line L10, the second control line L20, the third
control line L30, and the fourth control line L40). And, the
control device 390 may store some data serving as the first control
information, the data representing the plurality of control lines
(the first control line L10, the second control line L20, the third
control line L30, and the fourth control line L40). Moreover, the
control device 390 may store a parameter serving as the first
control information, the parameter being used for obtaining the
plurality of control lines (the first control line L10, the second
control line L20, the third control line L30, and the fourth
control line L40). Thus, the first control information is not
limited to a specific type of information.
[0475] In addition, the fluid temperature, the engine revolution
speed, and the temperature-restricting pressure are not limited to
the values (the threshold values) shown in FIG. 15.
[0476] In each of the first control line 10L, the second control
line L20, the third control line L30, and the fourth control line
L40, the temperature-restricting pressure reduces in accordance
with reduction of the engine revolution speed from the maximum
value (2500 rpm).
[0477] In each of the first control line 10L, the second control
line L20, the third control line L30, and the fourth control line
L40, the temperature-restricting pressure is constant in a case
where the engine revolution speed is at a predetermined revolution
speed (2000 rpm) or more.
[0478] In each of the first control line 10L, the second control
line L20, the third control line L30, and the fourth control line
L40, the temperature-restricting pressure increases in accordance
with increment of the fluid temperature at the identical engine
revolution speed.
[0479] In addition, each of the plurality of the control lines
includes a reducing section 311 and a constant section 312. The
reducing section 311 reduces the temperature-restricting pressure
in accordance with the reduction of the engine revolution speed.
The constant section 312 keep the temperature-restricting pressure
constant regardless of the reduction of the engine revolution
speed.
[0480] The first pressure-setting circuit 390A monitors the engine
revolution speed detected by the revolution speed detection device
301 (referred to as a detected revolution speed) and monitors the
fluid temperature (a detected fluid temperature) detected by the
temperature detection device 302.
[0481] The first pressure-setting circuit 390A obtains the
temperature-restricting pressure on the basis of the detected
revolution speed, the detected fluid temperature, and the first
control information. That is, the first pressure-setting circuit
390A obtains the temperature-restricting pressure on the basis of
the plurality of fluid temperatures and the engine revolution
speeds, the engine revolution speeds being set based on the
plurality of fluid temperatures.
[0482] The control device 390 outputs a control signal to the
proportional valve 373, and thereby sets the
temperature-restricting pressure obtained by the first
pressure-setting circuit 390A. The control device 390 sets the
aperture of the proportional valve 373, and thereby changes the set
pressure of the relief valve 378 on the basis of the engine
revolution speed and the fluid temperature.
[0483] According to the hydraulic system described above, the first
pressure-setting circuit 390A increases the temperature-restricting
pressure of the relief valve 378 in a case where the fluid
temperature is 0.degree. C. or more and a viscosity of the
operation fluid is low, for example.
[0484] Thus, in a case where the viscosity of the operation fluid
is low, the displacements of the first variable displacement pump
253L and the second variable displacement pump 253R are varied in
accordance with the operation devices (the first operation device
247 and the second operation device 248, and thereby a traveling
speed of the work machine 1 is changed.
[0485] Meanwhile, in a case where the fluid temperature is
-30.degree. C. or less and the viscosity of the operation fluid is
high, the first pressure-setting circuit 390A reduces the
temperature-restricting pressure. In that case, the displacements
of the first variable displacement pump 253L and the second
variable displacement pump 253R are reduced, and thereby the
operation fluid is warmed up with the traveling speed of the work
machine 1 reduced.
[0486] In addition, the temperature-restricting pressure is reduced
depending on each of the fluid temperatures in a case where the
engine revolution speed is reduced. That is, in the case where an
output power of the engine is reduced, the displacements of the
first variable displacement pump 253L and the second variable
displacement 253R are reduced, and thereby the work machine 1 is
capable of continuing works.
[0487] Meanwhile, the work machine 1 may restrict the traveling
speed of the work machine 1. FIG. 16 is a view illustrating a
hydraulic system (a hydraulic circuit) capable of restricting the
traveling speed. That is, FIG. 16 is a view illustrating a first
modified example of the hydraulic system described above.
[0488] In the restriction of the traveling speed, the control
device 390, the operation valve 370, or the like fixes an upper
value of the set pressure of the operation valve to a predetermined
value, and sets upper limitation values of the first variable
displacement pump 253L and the second variable displacement pump
253R. In this manner, even when the operation device is operated,
the traveling speed is restricted such that the traveling speed
does not exceeds a predetermined traveling speed. For convenience
of the explanation, the restriction of the traveling speed will be
referred to as a vehicle speed restriction.
[0489] For example, a restriction switch 303 is connected to the
control device 390, the restriction switch 390 being configured to
select whether to perform the vehicle speed restriction or not. The
restriction switch 303 may be a manual switch capable of being
operated by an operator and may be an automatic switch such as a
sensor capable of being switched automatically.
[0490] When the restriction switch 303 is turned on, the control
device 390 executes a process of the vehicle speed restriction.
When the restriction switch 303 is turned off, the control device
390 does not execute the process of the vehicle speed
restriction.
[0491] As shown in FIG. 16, the control device 390 includes a
second pressure-setting circuit (a second pressure-setting portion)
390B. The second pressure-setting circuit 390B is constituted of a
computer program stored in the control device 390, an electric
circuit, an electronic circuit, or the like, which are stored in
the control device 390.
[0492] The second pressure-setting circuit 390B sets the set
pressure of the relief valve 378 in the vehicle speed restriction.
For convenience of the explanation, the pressure of in the travel
fluid tube 245 is referred to as "a travel-restricting pressure",
the pressure being set in the vehicle speed restriction.
[0493] FIG. 16 is a view illustrating a relation between the engine
revolution speed, the fluid temperature, and the set pressures of
the relief valve 378 (the travel-restricting pressure, the
temperature-restricting pressure).
[0494] The control device 390 stores a second control information
(a second control map) showing a relation between the engine
revolution speed and the temperature-restricting pressure in the
vehicle speed restriction, for example. That is, the control device
390 has a fifth control line L50. The fifth control line L50 is
used in the vehicle speed restriction.
[0495] The fifth control line L50 sets an upper limitation of the
set pressure of the relief valve 378 in each of the first control
line L10, the second control line L20, the third control line L30,
and the fourth control line L40. The fifth control line L50 is a
control line that lowers the travel-restricting pressure than the
temperature-restricting pressure set by the first pressure-setting
circuit 390A.
[0496] In a case where the vehicle speed restriction is not
performed, the first pressure-setting circuit 390A sets the
temperature-restricting pressure on the basis of the plurality of
control lines (the first control line L10, the second control line
L20, the third control line L30, and the fourth control line L40).
For example, in a case where the engine revolution speed is in a
range Q10 on the control line L10 as shown in FIG. 17, the
temperature-restricting pressure is set to a range M10.
[0497] In addition, in a case where the engine revolution speed is
in a range Q20 on the control line L10, the temperature-restricting
pressure is set to a range M20. In a case where the vehicle speed
restriction is performed under that condition, the second
pressure-setting circuit 390B sets an upper limitation of the set
pressure (the speed-restricting pressure) of the relief valve 378
to a range M30 in accordance with the fifth control line L50.
[0498] That is, in a case where the vehicle speed restriction is
performed, the set pressure (the speed-restricting pressure) of the
relief valve 378 is fixed to the range M30 even when the engine
revolution speed is in the range Q10.
[0499] That is, in the case where the vehicle speed restriction is
performed, the second pressure-setting circuit 390B lowers the set
pressure (the travel-restricting pressure) of the relief valve 378
than the temperature-restricting pressure M10 and the range M20,
the temperature-restricting pressure M10 and the range M20 being
set the first pressure-setting circuit 390A.
[0500] In particular, the second pressure-setting circuit 390B
lowers the set pressure of the relief valve 378 than the
temperature-restricting pressure regardless of the fluid
temperature at any fluid temperature, 0.degree. C. or more,
-10.degree. C., -20.degree. C., -30.degree. C. or less.
[0501] As described above, the second pressure-setting circuit 390B
lowers the set pressure (the travel-restricting pressure) M30 of
the relief valve 378 than the range M20 and the
temperature-restricting pressure M10 set by the first
pressure-setting circuit 390A. In this manner, the operation fluid
can be supplied from the relief valve 378 to the operation fluid
tank 22 and the like even in the vehicle speed restriction, and
thereby the operation fluid is warmed up.
[0502] Meanwhile, the work machine 1 may restrict the engine
revolution speed. FIG. 18 is a view illustrating a hydraulic system
(a hydraulic circuit) capable of restricting the engine revolution
speed. That is, FIG. 18 is a view illustrating a second modified
example of the hydraulic system described above.
[0503] An accelerator 304 is connected to the control device 390.
The accelerator 304 is configured to set the engine revolution
speed. When the accelerator 304 is operated, an operation amount
(an operation extent) of the accelerator 304 is inputted to the
control device 390. Then, the control device 390 controls the
engine revolution speed in accordance with the operation amount of
the accelerator 304.
[0504] In a case where the engine revolution speed is restricted,
an upper limit of the engine revolution speed is set so as not to
exceed a restriction value Q40. The restriction value Q40 is a
value lower than the maximum value of the revolution speed of the
engine.
[0505] That is, in a case where the engine revolution speed is not
restricted, the engine revolution speed can be set to the
restriction value Q40 or more by the operation of the accelerator.
However, in a case where the engine revolution speed is restricted,
the control device 390 fixes the upper limit of the engine
revolution speed to the restriction value Q40 regardless of the
operation of the accelerator 304.
[0506] The accelerator 304 is not described in the embodiment
described above. However, the work machine 1 is provided with the
accelerator 304 obviously.
[0507] The engine revolution speed is restricted by the control
device 390. The engine revolution speed is restricted when the
fluid temperature detected by the temperature detection device 302
is lowered by a predetermined temperature or more, for example.
[0508] For convenience of the explanation, the pressure in the
travel fluid tube 245 will be referred to as "a revolution speed
restricting pressure (a rev.-restricting pressure)" below, the
pressure being set under the restriction of the engine revolution
speed. In addition, the restriction of the engine revolution speed
will be referred to as "a revolution speed restriction" below.
[0509] As shown in FIG. 18, the control device 390 includes a third
pressure-setting circuit (a third pressure-setting portion) 390C.
The third pressure-setting circuit 390C is constituted of a
computer program stored in the control device 390, an electric
circuit, an electronic circuit, or the like, which are stored in
the control device 390. The third pressure-setting circuit 390C
sets the set pressure of the relief valve 378 in the revolution
speed restriction.
[0510] FIG. 19 is a view illustrating a relation between the engine
revolution speed, the fluid, the set pressures (the
temperature-restricting pressure, the rev.-restricting pressure) of
the relief valve 378.
[0511] As shown in FIG. 19, the control device 390 stores a sixth
control line L60 and a seventh control line L70. The sixth control
line L60 is used in a case where the fluid temperature is a normal
temperature or more (for example, -10.degree. C. or more). The
seventh control line L70 is used in a case where the fluid
temperature is out of the normal temperature (for example, less
than -10.degree. C.).
[0512] The sixth control line L60 is used in a case where the fluid
temperature is the normal temperature when the revolution speed
restriction is not performed. The seventh control line L70 is used
in a case where the fluid temperature is out of the normal
temperature when the revolution speed restriction is performed.
[0513] The upper limit of the engine revolution speed shown in the
seventh control line L70 is identical to the restriction value Q40
employed in the revolution speed restriction. Additionally, under
the restriction value Q40, that is, in the range Q3 where the
revolution speed restriction is not performed. the rev.-restricting
pressure set on the seventh control line L70 is lower than the
temperature-restricting pressure set on the sixth control line
L60.
[0514] In a case where the revolution speed restriction is not
performed, the first pressure-setting circuit 390A sets the
temperature-restricting pressure on the basis of the sixth control
line L60. On the other hand, in a case where the fluid temperature
is out of the normal temperature and less than -10.degree. C., the
third pressure-setting circuit 390C sets the rev.-restricting
pressure on the basis of the seventh control line L70.
[0515] For example, the control device 390 fixes the operation
amount of the accelerator 304 to the restriction value Q40 even
when the operation amount of the accelerator 304 is set to the
engine revolution speed exceeding the restriction value Q40. On the
other hand, the third pressure-setting circuit 390C fixes the
rev.-restricting pressure to the rev.-restricting pressure M40 on
the basis of the restriction value Q40 and the seventh control line
L70.
[0516] In addition, when the operation amount of the accelerator
304 is set to be less than the restriction value Q40, the third
pressure-setting circuit 390C sets the rev.-restricting pressure to
a range M50 in accordance with the engine revolution speed.
[0517] That is, in the revolution speed restriction, the third
pressure-setting circuit 390C lowers the rev.-restricting pressure
than the temperature-restricting pressure set by the first
pressure-setting circuit 390A within the range Q30 where the
revolution speed restriction is not performed.
[0518] As described above, the output powers of the variable
displacement pumps (the first hydraulic pump P100, the second
hydraulic pump P20) is suppressed under the revolution speed
restriction. Under than condition, the operation fluid is supplied
from the relief valve 378 to the operation fluid tank 22 and the
like, and thereby the operation fluid is warmed up.
[0519] The hydraulic system according to the embodiment easily
changes the displacement of the variable displacement pump
connected to the hydraulic circuit for travel.
Seventh Embodiment
[0520] FIG. 20 is a view illustrating the hydraulic system
according to a seventh embodiment of the present invention.
Explanations of the configurations similar to the configurations of
the embodiments described above will be omitted. The seventh
embodiment is different from the sixth embodiment in that the first
operation device 247 provides a working operation and the second
operation device 248 provides a traveling operation.
[0521] The first operation device 247 is provided with an operation
valve 255A, an operation valve 255B, an operation valve 255C, and
an operation valve 255D, which are working-operation valves.
[0522] A first working fluid tube (a first working fluid path) 246a
connects the operation valve 255A to the pressure-receiving portion
of the first control valve 256A. A second working fluid tube (a
second working fluid path) 246b connects the operation valve 255B
to the pressure-receiving portion of the first control valve
256A.
[0523] A third working fluid tube (a third working fluid path) 246c
connects the operation valve 255C to the pressure-receiving portion
of the second control valve 256B. A fourth working fluid tube (a
fourth working fluid path) 246d connects the operation valve 255D
to the pressure-receiving portion of the second control valve
256B.
[0524] The operation valve 255A, the operation valve 255B, the
operation valve 255C, and the operation valve 255D are the working
operation valves.
[0525] The second operation device 248 is provided with an
operation valve 259A, an operation valve 259B, an operation valve
259C, and an operation valve 259D, which are traveling-operation
valves. The operation valve 259A, the operation valve 259B, the
operation valve 259C, and the operation valve 259D are connected to
a plurality of high-pressure select valves (shuttle valves) 321,
322, 323, and 324 by a fifth travel fluid tube 245d.
[0526] A first travel fluid tube 245a connects the shuttle valve
322 to the forward-movement pressure-receiving portion 253a of the
travel pump 253L. A second travel fluid tube 245b connects the
shuttle valve 324 to the backward-movement pressure-receiving
portion 253b of the travel pump 253L.
[0527] A third travel fluid tube 245c connects the shuttle valve
321 to the forward-movement pressure-receiving portion 253a of the
travel pump 253R. A fourth travel fluid tube 245d connects the
shuttle valve 323 to the backward-movement pressure-receiving
portion 253b of the travel pump 253R. The other configurations are
similar to the configurations of the sixth embodiment.
[0528] As described above, even in the hydraulic circuit that has
the first operation device 247 for the working operation and the
second operation device 248 for the traveling operation, the
hydraulic circuit is capable of changing the displacement of the
first variable discharge pump 253L and the displacement of the
second variable discharge pump 253R by discharging the operation
fluid included in the travel fluid tube 245 through the discharge
fluid tube 251 and the operation valve 370 on the basis of the
engine revolution speed and the fluid temperature.
[0529] A hydraulic system for a work machine includes a prime
mover, a variable displacement pump to be driven by a power of the
prime mover, the variable displacement pump being configured to
change a displacement of the variable displacement pump, an
operation device having an operation member and an operation valve
configured to change a pressure of the operation fluid in
accordance with an operation of the operation member, the operation
device being configured to change the displacement of the variable
displacement pump with use of the pressure of the operation fluid
changed by the operation valve, a travel fluid tube connecting the
operation valve to the variable displacement pump, a discharge
fluid tube connected to the travel fluid tube, the discharge fluid
tube being configured to discharge (drain) the operation fluid
included in the travel fluid tube, an operation valve disposed on
the discharge fluid tube, the operation valve being configured to
reduce the pressure of the operation fluid in the travel fluid
tube, and a control device (a controller) configured to control the
operation valve on the basis of a revolution speed of the prime
mover and a temperature of the operation fluid.
[0530] A hydraulic system for a work machine includes a prime
mover, a first variable displacement pump to be driven by a power
of the prime mover, the first variable displacement pump being
configured to change a displacement of the first variable
displacement pump, a second variable displacement pump to be driven
by a power of the prime mover, the second variable displacement
pump being configured to change a displacement of the second
variable displacement pump, a first operation device having a first
operation member and a first operation valve configured to change a
pressure of the operation fluid in accordance with an operation of
the first operation member, the first operation device being
configured to change the displacement of the variable displacement
pump with use of the pressure of the operation fluid changed by the
first operation valve, a second operation device having a second
operation member and a second operation valve configured to change
a pressure of the operation fluid in accordance with an operation
of the second operation member, the second operation device being
configured to change the displacement of the variable displacement
pump with use of the pressure of the operation fluid changed by the
second operation valve, a travel fluid tube connecting the first
operation valve and the second operation valve to the first
variable displacement pump and the second variable displacement
pump, a discharge fluid tube connected to the travel fluid tube,
the discharge fluid tube being configured to discharge (drain) the
operation fluid included in the travel fluid tube, an operation
valve disposed on the discharge fluid tube, the operation valve
being configured to reduce the pressure of the operation fluid in
the travel fluid tube, and a control device (a controller)
configured to control the operation valve on the basis of a
revolution speed of the prime mover and a temperature of the
operation fluid.
[0531] The control device includes a first pressure-setting circuit
configured to set a temperature-restricting pressure that is a
pressure in the travel fluid tube on the basis of a temperature of
the operation fluid and a revolution speed of the prime mover,
wherein the operation valve is controlled on the basis of the
temperature-restricting pressure.
[0532] The control device includes a first pressure-setting circuit
configured to set a temperature-restricting pressure that is a
pressure in the travel fluid tube on the basis of a plurality of
threshold values related to the operation fluid and revolution
speeds of the prime mover set in accordance with the plurality of
threshold values, wherein the operation valve is controlled on the
basis of the temperature-restricting pressure.
[0533] The control device includes a second pressure-setting
circuit configured to set a travel-restricting pressure in
restricting a traveling speed of the work machine, the
travel-restricting pressure being a pressure in the travel fluid
tube, wherein the second pressure-setting circuit lowers the
travel-restricting pressure than the temperature-restricting
pressure set by the first pressure-setting circuit in restricting
the traveling speed.
[0534] The control device includes a third pressure-setting circuit
configured to set a revolution-restricting pressure in restricting
the revolution speed of the prime mover, the revolution-restricting
pressure being a pressure in the travel fluid tube, wherein the
operation valve is controlled on the basis of the
revolution-restricting pressure.
[0535] The third pressure-setting circuit lowers the
revolution-restricting pressure than the temperature-restricting
pressure in restricting the revolution speed of the prime mover,
the temperature-restricting pressure being set by the first
pressure-setting circuit in a range of revolution speed where the
revolution speed of the prime mover is not restricted.
[0536] The hydraulic system according to the embodiment easily
changes the displacement of the variable displacement pump
connected to the hydraulic circuit for travel.
[0537] In the above description, the embodiment of the present
invention has been explained. However, all the features of the
embodiments disclosed in this application should be considered just
as examples, and the embodiments do not restrict the present
invention accordingly. A scope of the present invention is shown
not in the above-described embodiments but in claims, and is
intended to include all modifications within and equivalent to a
scope of the claims.
* * * * *